OFFICE LEASE BETWEEN SUNFUELS AND SIGNATURE CENTRE

E XHIBIT 10.29

O FFICE L EASE

S IGNATURE C ENTRE AT D ENVER W EST

14143 D ENVER W EST P ARKWAY

D ENVER , CO 80401

By and Between

S IGNATURE C ENTRE AT D ENVER W EST LLC

A D ELAWARE LIMITED LIABILITY COMPANY

(“ L ANDLORD ”)

And

S UN F UELS I NC .

A C OLORADO C ORPORATION

(“ T ENANT ”)

Dated As Of

M AY  25 2007

O FFICE B UILDING L EASE

O FFICE L EASE F ACING P AGE

THIS OFFICE LEASE FACING PAGE, together with the General Lease Provisions and any Riders, Exhibits, Schedules and Lease Guaranties attached hereto and initialed by the parties, will constitute the Lease between Tenant described above, as Tenant, and SIGNATURE CENTRE AT DENVER WEST LLC, as Landlord, for the Premises described above, made and entered into as of the Lease Date specified above.

T ABLE OF C ONTENTS

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A TTACHMENTS

E XHIBIT A – O FFICE L EASE A DDITIONAL P ROVISIONS

E XHIBIT B – T ENANT W ORK L ETTER AND D ESIGN G UIDELINES /E NVIRONMENTAL P OLICIES

E XHIBIT C – R ULES AND R EGULATIONS

E XHIBIT D – L EASE C ONFIRMATION R IDER

E XHIBIT E – S PACE P LAN (A TTACHED , D EPICTING ALL S PACE B EING L EASED ON F IRST F LOOR )

E XHIBIT F – L EGAL D ESCRIPTION OF R EAL P ROPERTY

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O FFICE B UILDING L EASE

G ENERAL L EASE P ROVISIONS

In consideration of the Rent and the covenants and agreements hereinafter made on the part of the Tenant to be paid, observed and performed, the Landlord has demised and hereby leases to the Tenant, the Leased Premises described on the Office Lease Facing Page attached hereto and outlined in the Space Plan attached hereto as Exhibit E comprising approximately 7.602 square feet of space and located on the first floor of the building at 14143 Denver West Parkway, Lakewood, Colorado (the “ Building ”) and more particularly described on Exhibit F attached hereto (the “ Real Property ”), but excluding therefrom any part of the exterior face of the Building, together with the right of the Tenant, in common with the Landlord, its other tenants, subtenants and invitees thereof, to the nonexclusive use of the following portions of the Building:

(a) The entrance foyer and lobby of the Building;

(b) The common corridors on the floor of the Building on which the Leased Premises are situated; together with public entrance doors, halls, stairways, passages, shipping and receiving areas and lavatories in the Building;

(c) The Building grounds and parking area.

In this Lease the following terms or words will have the following meanings.

(a) The terms appearing on the Office Lease Facing Page attached hereto will have the meanings stated thereupon.

(b) “ Herein ”, “ hereof ”, “ hereby ”, “ hereunder ”, “ hereto ”, “ hereinafter ” and similar expressions refer to this Lease and not to any particular paragraph, section or other portion thereof, unless the context otherwise specifies.

(c) “ Business Day ” means any of the days from Monday to Friday of each week inclusive unless such day is a holiday.

(d) “ Commencement Date ” means the later of (i) the date so designated on the Office Lease Facing Page attached hereto, or (ii) the date of Substantial Completion.

(e) “ Substantial Completion” means the date on which Landlord has completed the Tenant Improvements in accordance with the Tenant Improvement Plans and Specifications, subject to punch-list items that would not prevent the Tenant’s use or occupancy of the Leased Premises, and is not dependent upon whether Tenant has received any approvals Tenant may require specific for Tenant’s business. If Landlord has not substantially completed construction of the Building on or prior to October 31, 2007, then either party will have the right to terminate this Lease prior to substantial completion of construction of the Building upon written notice to the other party and this Lease will be null and void and Landlord and Tenant will be released from all further obligations under this Lease. If the Commencement Date is different than the date designated on the Office Lease Facing Page then Landlord and Tenant will include the Commencement Date in the Lease Confirmation Rider to be executed on or about the Commencement Date.

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(f) “ Lease Confirmation Rider ” means the document, substantially in the form set out in Exhibit D to this Lease, that sets out the essential elements of the terms of this Lease as of the Commencement Date.

(g) “ Normal Business Hours ” means the hours from 6:00 AM to 7:00 PM on Business Days and the hours of 8 a.m. to 1 p.m. on Saturdays unless Saturday is a holiday.

(h) “ Operating Costs ” has the meaning set forth in Section 7.1(c)(i).

(i) “ Prime Rate ” will mean the prime rate of interest published in the Western Edition of The Wall Street Journal or any successor publication from time to time, adjusted for any change in such prime rate, provided that if neither The Wall Street Journal nor any successor publication is published, any publication of bank or other lending institution prevailing rates of interest charged to most favored customers reasonably selected by the landlord.

(j) “ Real Estate Taxes ” has the meaning set forth in Section 7.1(b)(i).

(k) “ Rent ”, as the term is used throughout this Lease, will denote the “Base Rent”, as is described in Section 4, and all other financial obligations of the Tenant hereunder which are herein described as “Additional Rental” or “Additional Rent”.

(l) “ Rentable Square Footage ” will mean square footage determined by Landlord’s architect, acting consistently and reasonably, applying measurement standards promulgated by BOMA International The initial Rentable Square Footage of the Leased Premises and the Building will be confirmed in a Lease Confirmation Rider between the Landlord and the Tenant, executed on or about the Commencement Date. Rentable Square Footage may be remeasured by Landlord’s architect and adjusted by written notice from the Landlord to the Tenant if the Rentable Square Footage of the Leased Premises or the Building changes during the Term.

(m) “Tenant Work Letter” means the Tenant Work Letter and Design Guidelines attached to this Lease as Exhibit B and incorporated herein by reference. “Tenant Improvements” comprise those alterations to and installations in the Leased Premises that are set out in the Tenant Work Letter and any amendments to the Tenant Work Letter as are agreed to by the Landlord in writing subsequent to the Substantial Completion Date.

(n) “ Term ” means the number of years and months in the Initial Term, set forth on the Office Lease Facing Page attached hereto, to be computed from 12 o’clock noon on the Commencement Date and expiring at 12 o’clock noon the last day of such Lease Period together with any extension thereof pursuant to the provisions of Exhibit A , Section 1.

Tenant will have the right to have and hold the Leased Premises for and during the Term subject to the payment of the Base Rent and the Additional Rent and the full and timely performance by Tenant of the covenants and conditions hereinafter set forth.

4.1 Tenant covenants and agrees to timely pay without notice, deduction, offset or abatement to the Landlord at the Building, or such other address as Landlord may notify Tenant of in writing, yearly and every year during the Term hereof, the annual Base Rent in lawful money of the United States, payable in the monthly installments set forth in Section 4.2 hereof each month, in advance on the first day of each month during the Term hereof. If the Term hereof commences on any day other than the first day or expires on any day other than the last day of a month, Base Rent for the fractions of a month at the commencement and at the end of the Term will be adjusted pro rata on a per diem basis.

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4.2 Commencing on the Commencement Date the annual base rent (“ Base Rent ”) for each year during the Initial Term shall be determined in accordance with the following schedule:

Tenant will commence its business in the Leased Premises on the Commencement Date and thereafter will operate its business in the Leased Premises in compliance with the provisions of this Lease, and applicable governmental laws and regulations provided that nothing in this section will require the Tenant to carry on business during any period prohibited by any law or ordinance regulating or limiting the hours during which such business may be carried on.

6.1 Tenant will fully and timely pay all business and other taxes, charges, rates, duties, assessments and license fees levied, imposed, charged or assessed against or in respect of the Tenant’s occupancy of the Leased Premises or in respect of the personal property, trade fixtures, furniture and facilities of the Tenant or the business or income of the Tenant on and from the Leased Premises, if any, as and when the same become due, and will indemnify and hold Landlord harmless from and against all payment of such taxes, charges, rates, duties, assessments and license fees and against all loss, costs, charges and expenses occasioned by or arising from any and all such taxes, rates, duties, assessments and license fees. Notwithstanding the foregoing Tenant shall have the right to contest any of the items enumerated in Section 6.1 provided that such contest is promptly commenced and diligently pursued to completion and will not result in a lien on any portion of the building.

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6.2 Upon receipt of a written request from Landlord, Tenant will promptly deliver to Landlord for inspection receipts for payment of all taxes, charges, rates, duties, assessments and licenses in respect to all improvements, equipment and facilities of the Tenant on or in the Leased Premises which were due and payable up to one year prior to such request, and in any event to furnish to the Landlord, if requested by the Landlord, evidence, reasonably satisfactory to the Landlord of any such payments. Landlord will have no obligation hereunder or otherwise to make or monitor the making of such payments. Landlord shall not provide a written notice under this Section 6.2 more than once every six (6) calendar months.

Assuming that the Building is fully assessed and ninety five percent (95%) occupied, the Landlord estimates that the Tenant’s pro rata share of Real Estate Taxes and Operating Costs will be $7.90 per rentable square foot per year. The Landlord will cap increases in controllable Operating Costs at five percent (5%) per annum. Controllable expenses will include all expenses for the operation and maintenance of the Building except for Real Estate Taxes, property taxes, insurance, utilities and unforeseeable major equipment failures.

7.1 Real Estate Taxes and Operating Costs

(a) Tenant will pay to the Landlord as Additional Rent, a portion of the Real Estate Taxes and a portion of the Operating Costs, both of which are to be determined as follows:

(b)(i) “ Real Estate Taxes ” will mean and include all general and special taxes, assessments, duties and levies, charged and levied upon or assessed against the Building, the Real Property, any improvements situated on the Real Property, whether owned by Landlord or Tenant, not paid directly by the Tenant. Further, if at any time during the Term of this Lease the method of taxation of real estate prevailing at the time of execution hereof will be, or has been, altered so as to cause the whole or any part of the taxes now or hereafter levied, assessed or imposed upon real estate to be levied, assessed or imposed upon Landlord, wholly or partially, as a capital levy or otherwise, or on or measured by the rents received therefrom then such new or altered taxes attributable to the Leased Premises will be deemed to be included within the term Real Estate Taxes for purposes of this Section, save and except that such will not be deemed to include any increase in said tax not attributable to the Building.

(ii) The amount of Real Estate Taxes attributed to the Leased Premises for any year or portion of year will be the amount of such taxes determined by dividing the Rentable Square Footage of the Leased Premises by the total Rentable Square Footage in the Building and multiplying the resultant percentage by the total Real Estate Taxes. If the Building is part of a building complex not separately assessed for property tax purposes, taxes will be apportioned by the Landlord among the buildings in the complex in proportion to the Rentable Square Footage of each building. Landlord and Tenant will confirm the total Rentable Square Footage in the Leased Premises and the Building and such percentage in a Lease Confirmation Rider to be executed on or about the Commencement Date.

(c)(i) The term “ Operating Costs ” means the total amounts paid or payable, whether by the Landlord or others on behalf of the Landlord, in connection with the ownership, maintenance, repair, and operation of the Building, including without limiting the generality of the foregoing, the aggregate of the amount paid for all fuel used in heating and air conditioning of the Building, the purchase of energy for heating or other purposes; the amount paid or payable for all electricity furnished by the Landlord to the Building; the amount paid or payable for replacement of electric light bulbs, tubes and ballasts; the amount paid or payable for all hot and cold water (other than that paid by tenants of the Building directly) and sewer service; the amount paid or payable for any other utility or service provided to the Building or its grounds; the amount paid or payable for all labor and/or wages and other payments including cost to Landlord

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of workmen’s compensation and disability insurance, payroll taxes, welfare and fringe benefits made to janitors, landscapers, gardeners, caretakers, and other employees, contractors and subcontractors of the Landlord (including but not limited to salary or wages of the building manager) involved in the operation, maintenance, and repair of the Building, managerial and administrative expenses related to the Building; the total charges of any independent contractors employed in the repair, care, operation, maintenance, and cleaning of the Building; the amount paid or payable for all supplies including all supplies and necessities which are occasioned by everyday wear and tear; the costs of climate and energy management control systems, window and exterior wall cleaning, painting and repair, maintenance and repair to the common areas, including but not limited to replacement of landscaping and resurfacing, restriping and refilling parking areas, telephone costs; the cost of accounting services necessary to compute the rents and charges payable by tenants of the Building; fees for management, legal, accounting, inspection and consulting services, the cost of guards and other protection services; payments for general maintenance and repairs to the plant and equipment supplying climate control; the amount paid for premiums for all insurance; and all amounts payable in accordance with ground leases, easements, or rights-of-way appurtenant to the Building. Operating Costs will not, however, include interest on debt, capital retirement of debt, depreciation, costs properly chargeable to capital account in accordance with generally accepted accounting practices applicable to office buildings, and costs directly charged by the Landlord to any tenant or tenants. [Notwithstanding anything contained herein to the contrary, Operating Costs shall not include (1) depreciation on the Building (other than depreciation on personal property, equipment, window coverings on external windows provided by Landlord and carpeting, if any, in corridors and common areas), (2) costs of alterations of space or other improvements made for other tenants of the Building, (3) finders’ fees and real estate brokers’ commissions, (4) ground lease payments, mortgage principal or interest, (5) capital items other than those referred to in this Section 7.1(c)(i) above, (6) costs of replacements to personal property and equipment for which depreciation costs are included as an Operating Cost (7) costs of excess or additional services provided to any tenant in the Building which are directly billed to such tenant, (8) the costs of repairs due to casualty or condemnation which are reimbursed by third parties, (9) any costs due to Landlord’s breach of this Lease, (10) any income, estate, inheritance, or other transfer tax and any excess profit, franchise, or similar taxes on Landlord’s business, (11) all costs, including, but not limited to legal fees, relating to activities for the solicitation and executed of leases of space in the Building, and (12) any legal fees incurred by Landlord in enforcing its rights under other leases for premises in the Building. The reference to “ Building ” in this Lease will include all related facilities, including corridors, lobbies, arcades, sidewalks, grounds, and other public areas contained in or around the Building, as well as landscaping, parking areas, and exterior walkways and areas.

(i) The amount of Operating Costs attributed to the Leased Premises for any year or portion of year will be determined by dividing the Rentable Square Footage of the Leased Premises by the total Rentable Square Footage in the Building and multiplying the resultant percentage by the total of such Operating Costs. If the Building is part of a building complex owned by the Landlord, Operating Costs will be apportioned by the Landlord among the buildings in the complex in proportion to the Rentable Square Footage. Landlord and Tenant will confirm the total Rentable Square Footage in the Leased Premises and the Building and such percentage in a Lease Confirmation Rider to be executed on or about the Commencement Date.

(d) Excess Usage. “Excess Usage” means usage of Building service, including but not limited to utilities and HVAC, outside Normal Business Hours or in excess of the amount of such services that Landlord reasonably determines to be typical for the Building. If the Tenant wishes Excess Usage of the HVAC, i.e., use outside normal business hours, Tenant will pay to Landlord an hourly fee for such Excess Usage in such amount reasonably established by Landlord from time to time on a uniform basis for all tenants in the Building, taking into consideration the square footage occupied by such tenants. Tenant will pay for all such Excess Usage during the Term, as Additional Rent. All invoices for such Excess Usage will be due and payable upon receipt.

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(e) If only part of the final calendar year is included within the Term, the amount of Real Estate Taxes and Operating Costs payable by the Tenant for such period will be estimated by the Landlord acting reasonably and adjusted proportionately on a per diem basis and will be payable upon demand as soon as such amount has been ascertained by the Landlord.

(f) The Landlord will use generally accepted accounting practices, computed on an accrual basis, consistently applied, in calculating Operating Costs, Excess Usage and any other elements of Additional Rent.

7.2 Payment of Additional Rent.

Any Additional Rent payable by the Tenant under Section 7.1 hereof will be paid as follows, unless otherwise provided:

(a) During the Term, the Tenant will pay to the Landlord at the same time as the payment of the Base Rent, one-twelfth (1/12th) of the amount of such Additional Rentals estimated by the Landlord in advance, acting reasonably, to be due from the Tenant for a twelve month period of time. Such estimate may be adjusted from time to time by the Landlord, as actual Real Estate Taxes and Operating Costs become known, and the Tenant will pay installments of Additional Rentals according to such estimate, as periodically adjusted.

(b) Within ninety (90) days after the close of each calendar year, or as soon thereafter as practicable, the Landlord shall deliver to the Tenant a statement (“ Operating Statement ”) indicating the Operating Costs for the Building paid or incurred by the Landlord for the prior calendar year, the Tenant’s share thereof, and the amount that the Tenant owes, or is to be credited, for the prior year. Any Operating Statement shall be certified by Landlord. Unless otherwise contested by the Tenant in accordance with this paragraph, the Operating Statement shall be final and binding upon the Landlord and the Tenant. The Tenant shall have the right, within thirty (30) days of receipt of the Operating Statement to have an accountant employed or selected by Tenant’s Accountant (“Tenant’s Accountant”) review Landlord’s books and records relating to Operating Costs. Said review shall be conducted at the Landlord’s office designated on the Office Lease Facing Page during normal business hours and upon at least 48 hours advance notice. If Tenant’s Accountant uncovers discrepancies of greater than five percent (5%) in the aggregate in the calculation of any Operating Costs reflected in the Operating Statement, the Landlord shall bear the cost of the audit. Otherwise, the Tenant shall pay the fees of Tenant’s Accountant and shall accept the Landlord’s Operating Statement as binding.

(c) If the aggregate amount of such estimated Additional Rental payments made by the Tenant in any year of the Term should is less than the Additional Rentals due for such year of the Term, then the Tenant will pay to the Landlord as Additional Rent within ten (10) Business Days after demand the amount of such deficiency.

(d) If the aggregate amount of such Additional Rental payments made by the Tenant in any year of the Term is greater than the Additional Rentals due for such year, then the amount of such excess will be applied by the Landlord to the next succeeding installment of such Additional Rent due hereunder; and if there be any such excess for the last year of the Term, the amount thereof will be refunded by the Landlord to the Tenant within thirty (30) days after the amount of such excess becomes known or after the Term, whichever is sooner, provided that the Tenant is not otherwise in material default under the terms of this Lease.

(e) [intentionally omitted]

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Landlord will have the exclusive right to make any replacement of electric light bulbs, tubes and ballasts in the Leased Premises throughout the Term and any renewal thereof. The Landlord may adopt a system of relamping and reballasting periodically on a group basis in accordance with prudent practice.

Tenant will pay as Additional Rental, on demand, the reasonable cost of any metering which may be required by the Landlord to measure any Excess Usage.

10.1 Tenant’s use of electricity in the Leased Premises will be for the operation of standard lighting, electrical fixtures, desktop or laptop computers, photocopy machines, fax machines, scanners, printers, typewriters and other office machines and lamps, as well as agreed upon voice and data support space and equipment identified as part of Tenant Improvements, and will not at any time exceed the capacity of any of the electrical conductors and equipment in or otherwise serving the Leased Premises.

10.2 In order to ensure that such capacity is not exceeded and to avert possible adverse effect upon the Building’s electrical service, the Tenant will not, without the Landlord’s prior written consent in each instance, connect any additional fixtures, appliances or equipment (other than those items identified in Section 10.1) to the Building’s electric distribution system or make any alterations or additions to the electric system of the Leased Premises existing at the commencement of the Term. If the Landlord grants such consent, the cost of all additional risers and other equipment required therefor will be paid by Tenant to Landlord within ten (10) Business Days from receipt of written demand therefor. Furthermore, Tenant, at Landlord’s option, will pay within ten (10) days from receipt of written demand therefor, the cost of any electric current or other energy for the operation of main frame computer equipment or other equipment requiring more than is necessary for normal business use as reasonably determined by the Landlord.

11.1 If the Building members or elements of the Building used for the purpose of climate control of the Building, or if the water pipes, drainage pipes, electrical lighting or other equipment of the Building or the roof or outside walls of the Building or parking facilities of Landlord become damaged or are destroyed through the gross negligence or willful misconduct of the Tenant, its servants, agents, employees or anyone permitted by any of them to be in the Building, then the cost of the necessary repairs, replacements or alterations will be borne by the Tenant who will pay such cost to Landlord within ten (10) Business Days from receipt of written demand therefor.

11.2 Tenant will keep the Leased Premises in as good order, condition and repair as when they were entered upon, loss by fire or other casualty, unavoidable accident or ordinary wear and tear excepted. If Tenant fails to keep the Leased Premises in such good order, condition and repair as required hereunder to the reasonable satisfaction of Landlord, Landlord may provide Tenant with written notice describing the unsatisfactory conditions, if Tenant has failed to commence and actively pursue appropriate remedial actions reasonably calculated to cure such conditions within ten (10) Business Days following receipt of Landlord’s written notice, Landlord may restore the Leased Premises to such good order and condition and make such repairs without liability to Tenant for any loss or damage that may accrue to Tenant’s property or business by reason thereof, and upon completion thereof, Tenant will pay to Landlord, the costs of restoring the Leased Premises to such good order and condition and of the making of such repairs, within ten (10) days from receipt of written demand therefor.

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11.3 Tenant will deliver at the expiration of the Term hereof or sooner upon termination of the Term, the Leased Premises in the same condition as received, except for reasonable wear and tear between the last necessary repair, replacement and restoration made by the Tenant pursuant to its obligations hereunder, and cause to be removed at Tenant’s expense furniture and equipment belonging to Tenant, signs, notices, displays, and the like from the Premises and repair any damage caused by such removal.

11.4 Tenant will leave the Leased Premises at the end of each Business Day in a reasonably tidy condition for the purpose of allowing the performance of the Landlord’s cleaning services hereinafter described.

12.1 Tenant will not permit any part of the Leased Premises to be used or occupied by any persons other than the Tenant, any subtenants permitted under Section 12.2 and the employees of the Tenant and any such permitted subtenant, or permit any part of the Leased Premises to be used or occupied by any licensee or concessionaire, or permit any persons to be upon the Leased Premises other than the Tenant, such permitted subtenants, and their respective employees, customers and others having lawful business with them.

12.2 Tenant will not assign or sublet or part with the possession of all or part of the Leased Premises without the prior written consent of Landlord, which consent will not be unreasonably withheld; provided, however, that Tenant will submit in writing to Landlord (a) the name and legal composition of the proposed subtenant or assignee; (b) the nature of the business proposed to be carried on in the Leased Premises; (c) the terms and provisions of the proposed sublease; and (d) such financial and other information as the Landlord may reasonably request concerning the proposed subtenant or assignee. Any such consent to any assignment or subletting will not relieve the Tenant from its obligations for the payment of all Rent due hereunder and for the full and faithful observance and performance of the covenants, terms and conditions herein contained. Consent of the Landlord to an assignment or subletting will not in any way be construed to relieve the Tenant from obtaining the consent of the Landlord to any further assignment or subletting.

12.3 If the Tenant is a corporation, limited liability company, partnership or other entity, or if this Lease, with the consent of the Landlord as aforesaid, is assigned to a such an entity, and if at any time during the Term hereof, more than fifty percent (50.0%) of the shares or voting rights are transferred by sale, or assignment, bequest, inheritance, trust, operation of law or other disposition, or shares be issued so as to result in a change in the control of such entity by reason of ownership of greater than ten percent of the voting shares or otherwise, then and so often as such change of control will occur the Tenant will notify the Landlord in writing of such changes and the Landlord will have the right to terminate this Lease and the Term, at any time after such change of control by giving the Tenant sixty (60) days prior written notice of such termination. This Section 12.3 will not apply to the Tenant if at any time during the Term voting control of the Tenant is represented by shares listed on a national stock exchange or the NASDAQ Quotation System.

Tenant and its employees and all persons visiting or doing business with the Tenant in the Leased Premises will be bound by and will observe the reasonable Rules and Regulations promulgated from time to time by the Landlord relating to the Building and its grounds and parking lot of which notice in writing will be given to the Tenant and all such rules and regulations will be a default hereunder and Landlord will have all remedies provided for in this Lease in the event of default by Tenant. Landlord, however, will not be responsible to Tenant for nonobservance by any other tenant or person of any such Rules and Regulations, provided that Landlord has taken commercially reasonable steps to ensure that all such other tenants and persons are abiding by the Rules and Regulations. The Rules and Regulations in effect on the Lease Date are attached as Exhibit C .

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14.1 Except as expressly permitted by prior written consent of the Landlord, the Leased Premises will not be used other than for general business office purposes. All use of the Leased Premises will comply with the terms of this Lease and all applicable laws, ordinances, regulations or other governmental ordinances from time to time in existence.

14.2 Tenant agrees that it will not keep, use, sell or offer for sale in or upon the Leased Premises any article which may be prohibited by Landlord’s standard fire and extended coverage insurance policy in force from time to time covering the Building. In the event the Tenant’s occupancy or conduct of business in, or on the Leased Premises, whether or not the Landlord has consented to the same, results in any increase in premiums for such insurance carried from time to time by the Landlord with respect to the Building, the Tenant will pay any such increase in premiums as Additional Rental within ten (10) days after bills for such additional premiums will be rendered by the Landlord. In determining whether increased premiums are a result of the Tenant’s use or occupancy of the Leased Premises, a schedule issued by the organization computing the insurance rate, will be conclusive evidence of the several items and charges which make up such a rate. The Tenant will promptly comply with all reasonable requirements of the insurance authority or of any insurer now or hereafter in effect relating to the Leased Premises.

(a) Tenant will, during its occupancy of the Leased Premises and during the Term hereof, at its sole cost and expense, obtain, maintain and keep in full force and effect, and with the Tenant, the Landlord and the mortgagees of the Landlord named as beneficiaries therein as their respective interests may appear, the following types and kinds of insurance, in the amounts specified below or such other amounts as Landlord may from time to time reasonably request and which are customary for buildings similar to the Building in the Denver area:

(i) Upon property of every description and kind owned by the Tenant and located in the Building or for which the Tenant is legally liable or installed by or on behalf of the Tenant including, without limitation, furniture, fittings, installations, alterations, additions, partitions, fixtures and anything in the nature of a leasehold improvement insuring against loss to the extent of the full replacement value of that which is being covered, with coverage including sprinkler leakage (where applicable); and, in the event that there will be a dispute as to the amount which comprises full replacement value, the reasonable determination of the Landlord or the mortgagees of the Landlord will be conclusive.

(ii) Property damage and public liability insurance (including personal liability, contractual liability, tenants’ legal liability for the full replacement costs of the Leased Premises, and owners’ and contractors’ protective insurance coverage with respect to the Leased Premises and the Tenant’s use of any part of the Building) which coverage will include the business operations conducted by the Tenant and any other persons on the Leased Premises. Such policies will be written on a comprehensive basis with a single occurrence limit of not less than $1,000,000.

(b) All property damage policies written on behalf of the Tenant will contain a waiver of any subrogation rights which the Tenant’s insurers may have against the Landlord and against those for whom the Landlord, in law, is responsible whether any such damage is caused by the act, omission or fault of the Landlord or by those for whom the Landlord, in law, is responsible.

(c) All policies will be taken out with insurers reasonably acceptable to the Landlord and in form reasonably satisfactory from time to time to the Landlord. Insurance companies

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authorized to do business in the State of Colorado with a rating of A-XI or better as rated in the most recent edition of Best’s Insurance Reports will be deemed acceptable to Landlord. The Tenant agrees that certificates of insurance, or, if required by the Landlord or the mortgagees of the Landlord, certified copies of each such insurance policies will be delivered to the Landlord as soon as practicable after the placing of the required insurance, but in no event later than ten (10) days prior to Tenant taking possession of all or any part of the Leased Premises. All policies will contain an undertaking by the insurers to notify the Landlord and the mortgagees of the Landlord in writing not less than thirty (30) days prior to any material change, cancellation, or other termination thereof.

(d) [intentionally omitted]

(e) Tenant agrees that if Tenant does not take out and maintain the insurance specified above, Landlord may (but will not be required to) procure said insurance on Tenant’s behalf and charge Tenant the premium together with a fifteen percent handling charge, payable upon demand as Additional Rent.

If any insurance policy upon the Building or any part thereof will be cancelled or cancellation will be threatened or the coverage thereunder reduced or threatened to be reduced, in any way by reason of the use or occupation of the Leased Premises or any part thereof by the Tenant or by any assignee or subtenant of the Tenant or by anyone permitted by the Tenant to be upon the Leased Premises and, if the Tenant fails to remedy the condition giving rise to cancellation, threatened cancellation, or reduction of coverage, within twenty-four (24) hours after notice, the Landlord may, at its option, enter upon the Leased Premises and attempt to remedy such condition and the Tenant will pay the cost thereof to landlord within ten (10) days from receipt of written demand therefor. Such entry will not be deemed to be re-entry under Section 38.1(b) hereof and the Landlord will not be liable for any damage or injury caused to any property of the Tenant or of others located on the Leased Premises as a result of such entry. In the event that the Landlord will be unable to remedy such condition, then Landlord will have all of the remedies provided for in the Lease in the event of a default by Tenant. Notwithstanding the foregoing provisions of this Section 16, if Tenant fails to remedy as aforesaid, Tenant will be in default of its obligation hereunder and Landlord will have no obligation to attempt to remedy.

Tenant will comply with all provisions of law, including without limitation, federal, state, county and city laws, ordinances and regulations and any other governmental, quasi-governmental or municipal regulations which relate to the partitioning, equipment operation, alteration, occupancy and use of the Leased Premises, including but not limited to the Americans with Disabilities Act and hazardous materials laws, and to the making of any repairs, replacements, alterations, additions, changes, substitutions or improvements of or to the Leased Premises. Moreover, the Tenant will comply with all police, fire, and sanitary regulations imposed by any federal, state, county or municipal authorities and will observe and obey all governmental and municipal regulations governing the conduct of any business conducted in the Leased Premises.

(a) Tenant agrees that it will comply with all local, state and federal laws, rules and regulations dealing with the manufacture, generation, use, storage, treatment, transportation, disposal, release or removal of hazardous substances, materials, pollutants, contaminants, or wastes, including but not limited to the Comprehensive Environmental Response, Compensation and Liability Act (“ CERCLA ”), 42 U.S.C. 9601 et seq., the Federal Water Pollution Control Act, 33 U.S.C. 1231, et seq., the Emergency Planning and Community Right to Know Act, 33 U.S.C., 11000 et seq., the Resource Conservation and Recovery Act (“ RCRA ”), 42 U.S.C. 6901 et seq., the Clean Air Act, 42 U.S.C. 7401 et seq., as such laws may be amended or modified, whether

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such laws are presently in existence or promulgated during the Term, and all rules and regulations promulgated hereunder (“ Environmental Laws ”). Without limiting the foregoing, Tenant agrees that it will (i) give written notice to Landlord at least five (5) Business Days in advance of any manufacture, generation, use, storage, treatment, transportation, disposal, release or removal of Hazardous Substances from or on the Leased Premises, (ii) give written notice to Landlord within two (2) Business Days after receipt of any notice received by Tenant of violation, claim, suit or investigation relating to Hazardous Substances, (iii) immediately notify Landlord of any Hazardous Substance spill, release or discharge at or affecting the Leased Premises and promptly clean up any such spill, release or discharge in compliance with all applicable Environmental Laws, (iv) not use or employ the property, facilities, equipment or services of the Building or any complex of which the Building is a part to manufacture, generate use, transport, store, treat or dispose of or release Hazardous Substances, whether or not they were generated or produced on the Leased Premises, and (v) defend, indemnify and hold harmless Landlord against any and all claims, damage, liability and costs (including reasonable attorney and expert fees and cleanup costs) which Landlord may suffer, incur or pay resulting from or arising out of any manufacture, generation, use, storage, treatment, transportation, disposal, release or threat of release of Hazardous Substances from or on the Leased Premises or the Building or any complex of which the Building is a part or resulting from Tenant’s actions or actions of Tenant’s agents, employees, guests or invitees. “ Hazardous Substances ” means and includes all toxic or hazardous substances, materials, chemicals, contaminants, pollutants, and wastes of whatever kind or nature, regulated under, defined in, or listed in any Environmental Laws or requiring special handling under applicable laws, including but not limited to medical waste materials. Hazardous Substances include, without limitation, asbestos, PCBs, CFCs, petroleum and lead-based paint.

(b) If Tenant fails to fully comply with the terms of this Section, Landlord may, following the expiration of any applicable grace or cure period, at its option, perform any or all of Tenant’s obligations thereunder and all costs and expenses incurred by Landlord (including reasonable attorney fees and expert fees and cleanup costs) in connection therewith will be deemed to be Additional Rent payable by Tenant on demand therefor.

(c) [ Intentionally omitted ]

(d) The terms of this Section 18 will survive the expiration or termination of this Lease.

Tenant will not commit, suffer or permit any waste or damage or disfiguration or injury to the Leased Premises or common areas in the Building or the fixtures and equipment located therein or thereon, or permit or suffer any overloading of the floors thereof and will not place therein any safe, heavy business machinery, main frame computers, data processing machines, or other heavy things without first obtaining the consent in writing of the Landlord and, if requested, by Landlord’s superintending architect, and not use or permit to be used any part of the Leased Premises for any dangerous, noxious or offensive trade or business, and will not cause or permit any nuisance, noise or action in, at or on the Leased Premises.

Upon forty-eight (48) hours advance written notice (except in the case of a situation that Landlord reasonably believes to constitute an emergency situation requiring immediate access to the Leased Premises), Tenant agrees to and will permit the Landlord, its servants or agents to enter upon the Leased Premises at any time and from time to time for the purpose of inspecting and of making repairs, alterations or improvements to the Leased Premises or to the Building, or for the purpose of having access to the underfloor or ceiling ducts, or to the access panels to mechanical shafts (which the Tenant agrees not to obstruct), and the Tenant will not be entitled to compensation for any inconvenience,

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nuisance or discomfort occasioned thereby. The Landlord will also have the right of entry to remedy any condition which Landlord, in its reasonable discretion, believes may cause cancellation or reduction of any insurance maintained by Landlord on the Building. The Landlord will have the right to enter the Leased Premises in order to check, calibrate, adjust and balance controls and other parts of the heating, ventilating and climate control system at any time. The Landlord shall proceed hereunder in such manner reasonably calculated to minimize interference with the Tenant’s use and enjoyment of the Leased Premises.

For the purpose of this Section and for all other purposes set forth in this Lease, Landlord will have and retain a key with which to unlock all doors in, upon and about the Leased Premises and Landlord will have the right to use any and all means which Landlord may deem proper to open said doors in an emergency, in order to obtain entry to the Leased Premises.

Tenant will indemnify the Landlord and save it harmless from and against any and all loss (including loss of Rent payable by the Tenant or other tenants in the event of loss either directly or indirectly caused by commission or omission of Tenant), claims, actions, damages, liability and expenses in connection with loss of life, personal injury or damage to property arising from any occurrence in, upon or at the Leased Premises or any part thereof, or occasioned wholly or in part by the gross negligence or willful misconduct of the Tenant, its agents, contractors, employees, servants, licensees, or concessionaires or invitees or by anyone permitted to be on the Leased Premises by the Tenant. In case the Landlord will, without fault on its part, be made a part to any litigation commenced by or against the Tenant, then the Tenant will protect and hold the Landlord harmless and will pay all costs, expenses and reasonable attorneys’ fees incurred or paid by the Landlord in connection with such litigation.

Tenant will permit the Landlord or its agents to exhibit and show the Leased Premises to prospective tenants during normal Business Hours of the last six (6) months of the Term or any renewal thereof.

23.1 Tenant will not make, install or erect in or to the Leased Premises any installations, alterations, additions or partitions without submitting drawings and specifications therefor to the Landlord and obtaining the Landlord’s prior written consent in each instance. Furthermore, the Tenant will obtain the Landlord’s prior written consent to any change or changes in such drawings or specifications submitted as aforesaid, Tenant will pay the reasonable cost to the Landlord of having its architects review such plans and changes thereto prior to proceeding with any work based on such drawings or specifications. All such work will be performed free and clear of all mechanic’s liens and Landlord will have no liability for the performance of such work, notwithstanding its consent to any plans and specifications. Without limiting the generality of the foregoing any work performed by or for the Tenant will be performed by competent workmen whose labor union affiliations are not incompatible with those of any workmen who may be employed in the Building by the Landlord, its contractors or subcontractors. The Tenant will submit to the Landlord’s supervision over construction, will provide Landlord upon request with financial assurances prior to the commencement of alterations, and promptly pay to the Landlord’s or the Tenant’s subcontractors as the case may be, when due, the cost of all such work and of all materials, labor and services involved therein and of all decoration and all changes in the Building, its equipment or services necessitated thereby. The Tenant covenants that the Tenant will not suffer or permit during the Term hereof any mechanic’s or other liens for work, labor, services or materials ordered by the Tenant or for the cost of which the Tenant may be in any way obligated, to attach to the Leased Premises or to the Building and that whenever and so often as any such liens will attach or claims therefor will be filed, the Tenant will within

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twenty (20) days after the Tenant has notice of the claim for lien procure the discharge thereof by payment or by giving security or in such other manner as is or may be required or permitted by law or which will otherwise satisfy Landlord. The Tenant will, at its own cost and expense, take out or cause to be taken out any additional insurance or bonds reasonably required by the Landlord to protect the Landlord’s and the Tenant’s interest during the period of alteration.

23.2 At least five (5) days prior to the commencement of any work permitted to be done by persons requested by the Tenant on the Leased Premises, the Tenant will notify the Landlord of the proposed work and the names and addresses of the persons supplying labor and materials for the proposed work so that the Landlord may avail itself of the provisions of statutes such as §38-22-105(2) of the Colorado Revised Statutes as they exist on the Lease Date or are subsequently amended. During any such work on the Leased Premises, the Landlord or its representatives will have the right to go upon and inspect the Leased Premises at all reasonable times, and will have the right to post and keep posted thereon notices such as those provided for by §38-22-105(2) C.R.S. or to take any further action which the Landlord may deem to be proper for the protection of the Landlord’s interest in the Leased Premises.

23.3 Landlord will have the right to use and make changes or additions to the Building, the Common Areas and the Leased Premises including but not limited to the pipes, wires, conduits and ducts in the Leased Premises where necessary to serve other premises in the Building but not in any way so as to interfere materially with the use and enjoyment of the Leased Premises and the Landlord will repair any damage to the Leased Premises so caused. The Tenant will not unduly obstruct such pipes, conduits and ducts in the Leased Premises so as to prevent reasonable access thereto.

Tenant will pay on demand the cost of replacement of any glass broken on the Leased Premises including outside windows and doors of the perimeter of the Leased Premises (including perimeter windows in the exterior walls) during the continuance of this Lease, unless the glass is broken by the Landlord, its servants, employees or agents acting on its behalf. Said replacement will be with glass identical to the glass originally installed in the Building, or if no longer available, with as good specification, quality and size reasonably acceptable to the Landlord.

(a) Tenant will not place or permit to be placed in or upon the Leased Premises, where visible from outside the Building, or outside the Leased Premises any signs, notices, drapes, shutters, blinds or displays of any type without the prior written consent of Landlord.

(b) Landlord reserves the right in Landlord’s sole discretion to place and locate on any roof or exterior of the Building such signs, notices, displays and similar items as Landlord deems appropriate in the proper operation of the Building.

At Landlord’s option, this Lease will be subject to and subordinate to all mortgages (including any deed of trust and mortgage securing bonds and all indentures supplemental thereto) and to all underlying, superior, ground or land leases which may now or hereafter encumber the Real property of which the Leased Premises are a part, and all renewals, modifications, consolidations, replacements and extensions thereof of such mortgages and leases which may now or hereafter affect the Leased Premises or any part thereof. The Tenant hereby constitutes the Landlord the agent or attorney of the Tenant coupled with an interest for the purpose of executing any subordination, acknowledgment or agreement required by any mortgagee, lender or lessor of Landlord.

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Tenant agrees that it will at any time and from time to time upon not less than ten (10) Business Days’ prior notice execute and deliver to the Landlord a statement in writing certifying that this Lease in unmodified and in full force and effect (or, if modified, stating the modifications and that the same is in full force and effect as modified), the amount of the annual Rent then being paid hereunder, the dates to which the Rent, by installment or otherwise, and other charges hereunder have been paid, and whether or not there is any existing default on the part of the Landlord of which the Tenant has knowledge and such other factual information reasonably required by Landlord or its mortgagees.

28.1 Taking possession of the Leased Premises by Tenant will be conclusive evidence as against Tenant that the Leased Premises were in good and satisfactory condition when possession was taken, and acknowledgment of completion in full accordance with the terms of this Lease.

28.2 Tenant agrees that there is no promise, representation or undertaking by or binding upon the Landlord with respect to any alteration, remodeling or redecorating of or installation of equipment or fixtures in the Leased Premises, except such, if any, as are expressly set forth in this Lease, or the typical plan schedule attached hereto.

Landlord covenants and agrees with Tenant that upon Tenant paying Rent, Additional Rent and other monetary sums due under the Lease, and performing its covenants and conditions under the Lease, Tenant will and may peaceably and quietly have, hold and enjoy the Leased Premises for the Term, subject, however, to the terms of the Lease and of any of the ground leases, mortgages or deeds of trust referred to in Section 26.

30.1 Climate Control: Landlord will provide climate control to the Leased Premises during Normal Business Hours to maintain a temperature adequate for comfortable occupancy, except during the making of repairs, alterations or improvements Landlord shall take commercially reasonable steps to minimize the impact of any such repairs, alterations, or improvements during Normal Business Hours and provided that the Landlord will have no responsibility or liability for failure to supply climate control service when stopped as aforesaid or when prevented from doing so by strikes, governmental action or any cause beyond the Landlord’s reasonable control, including failure of any utility company to provide the Building with appropriate utility service. The Tenant acknowledges that the Landlord has installed in the Building a system for the purpose of climate control, which system is designed to heat and cool during normal occupancy of the Leased Premises as general offices based upon the window shading being fully closed in those offices having exterior windows exposed to the sun and without regard to the Tenant’s specific use thereof or the installation of any computers or data processing equipment. Any use the Leased Premises not in accordance with the design standards or arrangement of partitioning which interferes with the normal operation of such system may require changes or alterations in the system or ducts through which the same operates. Any changes or alterations so occasioned, as such changes can be accommodated by the Landlord’s equipment, will be made by the Tenant at its cost and expense but only with the prior written consent of the Landlord first had and obtained, and in accordance with drawings and specifications and by a contractor first approved in writing by the Landlord, at Tenant’s cost and expense. If installation of partitions, equipment or fixtures by the Tenant necessitates the re-balancing of the climate control equipment in the Leased Premises, the same will be performed by the Landlord at Tenant’s expense as Additional Rental payable on