Updated: Jul 07, 2026
Location and Projects
Address
1831 Boston Ave, Longmont, CO, 80501
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Welzig Mechanical
Welzig Mechanical, 1831 Boston Ave, Longmont, CO (Owned by: James Welzig) holds a Electrical Contractor license and 14 other licenses according to the Lafayette license board.
Their BuildZoom score of 110 ranks in the top 4% of 55,949 Colorado licensed contractors.
Their license was verified as active when we last checked. If you are thinking of hiring Welzig Mechanical, we recommend double-checking their license status with the license board and using our bidding system to get competitive quotes.
Welzig Mechanical Contact Information
Phone Number: (303) 678-5576
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Address: 1831 Boston Ave, Longmont, CO 80501
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Welzig Mechanical Longmont
Quality
110
96th percentile
Pro tip:
We generally recommend hiring a contractor with a score higher than 95.
Welzig Mechanical has a BuildZoom score of 110, which places them above 96% of 55,949 contractors in Colorado.
Activity
|
240 projects
|
2025 |
|
192 projects
|
2024 |
|
155 projects
|
2023 |
Our building permit records indicate that Welzig Mechanical has worked on at least
587.0 projects over the past 3 years.
This is an overview of this contractor's activity. Click here to access our complete licensing and building permit database.
This is an overview of this contractor's activity. Click here to access our complete licensing and building permit database.
Experience
|
37 projects
|
Home Additions |
|
485 projects
|
HVAC projects |
|
27 projects
|
Mechanical projects |
Analyzing permits over the last 4 years shows that Welzig Mechanical mostly works on
hvac project
and home addition
projects.
Pricing
|
149 projects
|
< $5k |
|
272 projects
|
$5k-$20k |
|
8 projects
|
$20k-$50k |
|
3 projects
|
$50k-$100k |
|
2 projects
|
$100k-$250k |
|
1 project
|
$500k-$1mil |
The typical size of their permits is approximately $6,500. This graph shows the distribution of these job values.
Pro tip:
For more details about their pricing, check out their recent activity to see how much they have charged for different types of work.
This is a sample of this contractor's permits. Click here to access their complete permit history.
Replace existing furnace with new 80% afue 80k btu furnace replace existing air conditioning system with 4 ton 16.5 seer heat pump system. must comply with 2021 irc ipc imc and 2023 nec. project is subject to field inspections. inspections will not be performed unless all permit documentation is printed out and on site. inspections will not be performed unless all installation manuals... see more
Valuation:
N/A
Permit #:
BP-25-01956
Status:
complete
Fee:
$488
Permit Type:
N/A
Building Type:
N/A
Replace air conditioning like for like. must comply with 2021 irc 2021 ipc and 2023 nec. work is subject to field inspections. inspections will not be performed unless all permit documentation is printed out and on site. inspections will not be performed unless all installation manuals are provided on site
Valuation:
N/A
Permit #:
BP-25-01391
Status:
issued
Fee:
$296
Permit Type:
N/A
Building Type:
N/A
Replace (2) existing furnaces with a new 80% afue 70 000 btu/hr furnace and 80% afue 90 000 btu/hr furnace. replace (2) existing air conditioning systems with a 2 ton 19.5 seer heat pump system and a 4 ton 20 seer air conditioning system
Valuation:
$25,600
Permit #:
B202501243
Status:
complete
Fee:
$100
Permit Type:
N/A
Building Type:
N/A
Basement finish - 1384 sf basement finish. previous framing and electrical done by others with no record of permit being issued. dhs will correct framing fire-block insulate drywall and finishes
Valuation:
$62,000
Permit #:
B202407702
Status:
complete
Fee:
$2,717
Permit Type:
N/A
Building Type:
N/A
Replacement forced air furnace for single-family detached residence
2025-08-21
Replace (2) existing furnaces with a new 80% afue 70 000 btu/hr furnace and a new 80% afue 90 000 btu/hr furnace. replace (2) existing air conditioning systems with a 2.5 ton 16 seer air conditioning system and a 3 ton 16 seer air conditioning system. **please note: applicable only to systems with fuel burning appliances: all new plastic glued vents for fuel burning appliances must un... see more
Valuation:
$0
Permit #:
MEC2025-01378
Status:
issued
Fee:
$0
Permit Type:
N/A
Building Type:
N/A
Remove & install 60k btu furnace & 2 ton air conditioning in crawlspace. must comply with 2021 irc ipc imc and 2023 nec. project is subject to field inspections. inspections will not be performed unless all permit documentation is printed out and on site
Valuation:
N/A
Permit #:
BP-25-02637
Status:
complete
Fee:
$665
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 80% afue 70 000 btu/hr furnace. replace existing air conditioning system with a new 16 seer 2.5 ton air conditioning system
Valuation:
$6,591
Permit #:
B202502671
Status:
complete
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 96% afue 100 000 btu/hr furnace. replace existing air conditioning system with a new 16 seer 4 ton air conditioning system
Valuation:
$12,852
Permit #:
B202501990
Status:
expired
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 80% afue 70 000 btu/hr furnace. replace existing air conditioning system with a new 16 seer 2.5 ton air conditioning system
Valuation:
$7,968
Permit #:
B202501552
Status:
complete
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 80% afue 70 000 btu/hr furnace. replace existing air conditioning system with anew 2.5 ton 14 seer air conditioning system
Valuation:
$7,969
Permit #:
B202500907
Status:
complete
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 80% afue 70 000 btu/hr furnace. replace existing air conditioning system with a new 15 seer 3 ton air conditioning system
Valuation:
$5,711
Permit #:
B202502877
Status:
complete
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 96% afue 80 000 btu/hr furnace. replace existing air conditioning system with a new 16 seer 3 ton air conditioning system
Valuation:
$11,025
Permit #:
B202502838
Status:
issued
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 98% afue 60 000 btu/hr furnace. replace existing air conditioning system with a new 15.2 seer 3 ton heat pump system
Valuation:
$16,271
Permit #:
B202502492
Status:
complete
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 80% afue 70 000 btu/hr furnace. replace existing air conditioning system with anew 3 ton 14 seer air conditioning system
Valuation:
$6,310
Permit #:
B202502482
Status:
complete
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 80% afue 70 000 btu/hr furnace. replace existing air conditioning system with a new 17 seer 3 ton air conditioning system
Valuation:
$11,213
Permit #:
B202502259
Status:
complete
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 80% afue 90 000 btu/hr furnace. replace existing air conditioning system with a new 4 ton 14 seer air conditioning system
Valuation:
$7,709
Permit #:
B202501983
Status:
complete
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 80% afue 70 000 btu/hr furnace. replace existing air conditioning system with anew 2.5 ton 16 seer air conditioning system
Valuation:
N/A
Permit #:
MEC2025-00632
Status:
issued
Fee:
N/A
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 96% afue 60 000 btu/hr furnace. replace existing air conditioning system with a new 2.5 ton 16 seer air conditioning system
Valuation:
N/A
Permit #:
MEC2025-00494
Status:
complete
Fee:
N/A
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 80% afue 70 000 btu/hr furnace. replace existing air conditioning system with a new 3 ton 16 seer air conditioning system
Valuation:
$9,742
Permit #:
B202500820
Status:
expired
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
Replace existing furnace with a new 80 000 btu/hr 96% afue furnace. replace existing air conditioning system with a new 18.5 seer 3 ton heat pump system
Valuation:
$10,479
Permit #:
B202502890
Status:
complete
Fee:
$50
Permit Type:
N/A
Building Type:
N/A
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Welzig Mechanical Reviews
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Verified License
BuildZoom confirmed this contractor's license
Welzig Mechanical License info
Verified License
| License # | 25-000441 |
| Status | Active |
| City | Lafayette |
| Type | Electrical Contractor |
- BuildZoom verified this license was active as of March 2026.
Verify this license's status for Welzig Mechanical at the City of Lafayette.
This is a sample of licensing data; click here to access a complete history.
Verified License
| License # | 21-099065 |
| Status | Active |
| City | Lafayette |
| Type | Mechanical Contractor |
- BuildZoom verified this license was active as of March 2026.
Verify this license's status for Welzig Mechanical at the City of Lafayette.
This is a sample of licensing data; click here to access a complete history.
Verified License
| License # | CL2940 |
| Status | Active |
| County | Larimer County, Co |
| Type | Mechanical Commercial |
| Class | Commercial |
| Date Issued | 11-21-2025 |
- BuildZoom verified this license was active as of July 2026.
Verify this license's status for Welzig Mechanical at the Larimer County.
This is a sample of licensing data; click here to access a complete history.
Verified License
| License # | LCC2015006718 |
| Status | Active |
| City | Thornton |
| Type | Class D Mechanical Expires 2026 09 11 |
- BuildZoom verified this license was active as of July 2026.
Verify this license's status for Welzig Mechanical at the Thornton City Development Contractor License.
This is a sample of licensing data; click here to access a complete history.
Verified License
| License # | LIC-0003640-MECHB |
| Status | Active |
| City | Boulder |
| Type | Mechanical |
| Class | Class B Commercial and Residential |
| Date Issued | 04-14-2026 |
- BuildZoom verified this license was active as of July 2026.
Verify this license's status for Welzig Mechanical at the Boulder Licensing Board.
This is a sample of licensing data; click here to access a complete history.
Verified License
| License # | 060630051 |
| Status | Active |
| City | Westminster |
| Type | General Contractor |
- BuildZoom verified this license was active as of July 2026.
Verify this license's status for Welzig Mechanical at the City of Westminster, Colorado.
This is a sample of licensing data; click here to access a complete history.
Verified License
| License # | CON-11-0231 |
| Status | Active |
| County | Boulder County |
| Type | Commercial Mechanical Installations And Repair |
- BuildZoom verified this license was active as of November 2025.
Verify this license's status for Welzig Mechanical at the Boulder County Land Use Department.
This is a sample of licensing data; click here to access a complete history.
License Not Verified
| License # | PLB4538281 |
| Status | Active |
| City | Lafayette |
| Type | Plumbing Contractor |
- When BuildZoom last verified this license, it had an expiration date of June, 2022. Check the current license status of Welzig Mechanical with the City of Lafayette
This is a sample of licensing data; click here to access a complete history.
License Not Verified
| License # | MEC0799065 |
| Status | Active |
| City | Lafayette |
| Type | Mechanical Contractor |
- When BuildZoom last verified this license, it had an expiration date of June, 2022. Check the current license status of Welzig Mechanical with the City of Lafayette
This is a sample of licensing data; click here to access a complete history.
License Not Verified
| License # | LIC-0003640 |
| Status | Active |
| City | Boulder |
| Type | Mechanical |
| Class | Class B Commercial & Residential |
- When BuildZoom last verified this license, it had an expiration date of December, 2018. Check the current license status of Welzig Mechanical with the Boulder Licensing Board
This is a sample of licensing data; click here to access a complete history.
License Not Verified
| License # | 0003640 |
| Status | Active |
| City | Boulder |
| Type | Mechanical Class B Commercial & Residential |
- When BuildZoom last verified this license, it had an expiration date of January, 2015. Check the current license status of Welzig Mechanical with the Boulder Licensing Board
This is a sample of licensing data; click here to access a complete history.
Inactive License
| License # | 21-038281 |
| Status | Inactive |
| City | Lafayette |
| Type | Plumbing Contractor |
- According to the City of Lafayette, the status of this license was at one point cancelled. However, this information may have changed. If this is your business, please update your license status.
Check this license's status for Welzig Mechanical at the City of Lafayette.
This is a sample of licensing data; click here to access a complete history.
Inactive License
| License # | AEC10201 |
| Status | Inactive |
| City | Arvada |
| Type | Contractor |
- According to the The City of Arvada, Colorado, the status of this license was at one point cancelled. However, this information may have changed. If this is your business, please update your license status.
Check this license's status for Welzig Mechanical at the The City of Arvada, Colorado.
This is a sample of licensing data; click here to access a complete history.
Inactive License
| License # | 4327 |
| Status | Inactive |
| State | Colorado |
| Type | Plumbing Contractor |
- According to the Colorado Division of Professions and Occupations, the status of this license was at one point cancelled. However, this information may have changed. If this is your business, please update your license status.
Check this license's status for Welzig Mechanical at the Colorado Division of Professions and Occupations.
This is a sample of licensing data; click here to access a complete history.
Inactive License
| License # | 4327 |
| Status | Inactive |
| State | Colorado |
| Type | Plumbing Contractor |
- According to the Colorado Division of Professions and Occupations, the status of this license was at one point cancelled. However, this information may have changed. If this is your business, please update your license status.
Check this license's status for Welzig Mechanical at the Colorado Division of Professions and Occupations.
This is a sample of licensing data; click here to access a complete history.
110
BuildZoom Score
3.2K
Permits
- Building permit records show that Welzig Mechanical has worked on 3207 permitted projects.
Welzig Mechanical Employees
CK
Carey King
Owner
CW
Casey Welzig
DG
David Kaplan Gomez
JW
James Welzig
Owner
JW
Jim Welzig
Contact
WI
Welzig Heating & Air, Inc.