Go Back   InterNACHI Inspection Forum > >

Notices

Texas/TPREIA Home Inspectors This is a place for Texas InterNACHI inspectors to discuss Texas home inspection topics. Become a home inspector in Texas

Reply
 
Thread Tools
  #1  
Old 11/30/17, 6:22 PM
Tim M. White Tim M. White is offline
InterNACHI Applicant
 
Join Date: Nov 2017
Posts: 2
Default AC condenser size and foam insulation

I have a question regarding AC condenser size and foam insulation. My understanding of the "Rule of Thumb" for condenser size is 400 - 500 sq ft per ton. If we have foam insulation the sq ft coverage per ton can go up to 800 sq ft. When we put foam on the rafters and bring the attic into the envelope, we're now including the cubic ft in the attic space to the equation.


The house is a 1 story, 3,300 sq ft, with 10' ceilings and a massive attic space. One 4 ton AC condenser for all. I recommended that the buyer ask for the design specs or consult an HVAC contractor for further evaluation.



I'm looking for 2 items:



1) Do you recommend even speaking to this kind of issue? Some inspectors here in TX say no. It's not in our Standards of Practice; But, neither is using IR cameras. (We use IR cameras).



2) I'd like some clarification on the Condenser size when foam is used at the rafters, bringing the attic into the building envelope. This is a mountain of conditioned space that comes into the equation. My HVAC guy didn't have an answer. The only thing I can think of is that, because the foam seals air leaks in the attic, we have fewer air changes and higher efficiency.



Any help would be hugely appreciated!


Thanks,
Tim

Last edited by twhite; 11/30/17 at 6:33 PM..
Reply With Quote
Need a home inspection in Oklahoma? Check out InterNACHI's listing of Oklahoma certified home inspectors. Or, find a home inspector anywhere in the world with our inspection search engine.
  #2  
Old 11/30/17, 6:27 PM
Roy Lewis, CMI's Avatar
Roy Lewis, CMI Roy Lewis, CMI is online now
Certified Master Inspector ®
 
Join Date: Nov 2012
Location: North Florida
Posts: 12,717
Default Re: AC condenser size and foam insulation

That is way beyond the scope of a home inspection..Yep!




InterNACHI Lifetime Member.
www.1stproinspection.com
roy@1stproinspection.com
Serving Gainesville Florida and surrounding areas.
Florida Certified Contractor #CRC1328001
Florida Certified Home Inspector #HI7019
Deus solus me iudicare potest
#1st Pro Inspection
Reply With Quote
  #3  
Old 11/30/17, 7:30 PM
Emmanuel J. Scanlan, TREC# 7593 Emmanuel J. Scanlan, TREC# 7593 is offline
Certified Professional Inspector (CPI)
 
Join Date: Dec 2004
Location: Josephine, TX
Posts: 7,078
Default Re: AC condenser size and foam insulation

Quote:
Originally Posted by twhite View Post
I have a question regarding AC condenser size and foam insulation. My understanding of the "Rule of Thumb" for condenser size is 400 - 500 sq ft per ton. If we have foam insulation the sq ft coverage per ton can go up to 800 sq ft. When we put foam on the rafters and bring the attic into the envelope, we're now including the cubic ft in the attic space to the equation.


The house is a 1 story, 3,300 sq ft, with 10' ceilings and a massive attic space. One 4 ton AC condenser for all. I recommended that the buyer ask for the design specs or consult an HVAC contractor for further evaluation.



I'm looking for 2 items:



1) Do you recommend even speaking to this kind of issue? Some inspectors here in TX say no. It's not in our Standards of Practice; But, neither is using IR cameras. (We use IR cameras).



2) I'd like some clarification on the Condenser size when foam is used at the rafters, bringing the attic into the building envelope. This is a mountain of conditioned space that comes into the equation. My HVAC guy didn't have an answer. The only thing I can think of is that, because the foam seals air leaks in the attic, we have fewer air changes and higher efficiency.



Any help would be hugely appreciated!


Thanks,
Tim
For question 1& 2 if you choose to exceed the SOP in this case be absolutely sure you can and are willing to perform the ACCA Manual J calculations.

Quote:
TREC Rules | TREC

For heating, ventilation, and air conditioning systems inspected under this section, the inspector is not required to perform the following actions:

determine:
  1. sizing, efficiency, or adequacy of the system;



Knowledge is power, but sharing knowledge brings peace!

http://www.psinspection.com

TREC License# 7593
ICC Residential Combination Inspector
#5247015-R5 (Electrical, Mechanical, Plumbing and Building)
Professional Real Estate Inspections for the counties of Collin, Rockwall, Hunt, Dallas, Tarrant, Kaufman and all surrounding areas. If you want the the best you will find it with PS Inspection & Property Services LLC!
Reply With Quote
  #4  
Old 11/30/17, 8:41 PM
David A. Andersen, TN HI# 40's Avatar
David A. Andersen, TN HI# 40 David A. Andersen, TN HI# 40 is offline
Certified Professional Inspector (CPI) ®
 
Join Date: Jun 2005
Location: Nashville, TN
Posts: 10,515
Default Re: AC condenser size and foam insulation

Quote:
My understanding of the "Rule of Thumb" for condenser size is 400 - 500 sq ft per ton.
Your kidding, right?!

"I recommended that You ask for the design specs or consult an HVAC contractor for further training."



David A. Andersen & Associates
Clarksville - Nashville Home Inspector Lic#40 (Retired)
ITC Level III Thermographer Cert#1958
Building Science Thermographer Cert#33784
HVAC Certification EPA Cert#2046620
BPI# 5015804
Reply With Quote
  #5  
Old 12/1/17, 1:15 AM
John Cahill, TREC 855 John Cahill, TREC 855 is offline
Certified Professional Inspector (CPI)
 
Join Date: Dec 2004
Location: Plano, TX
Posts: 1,077
Default Re: AC condenser size and foam insulation

Proper design of HVAC systems for spray foam homes

HVAC sizing and analysis

Lots more. Search Google AC sizing unvented attic

I depart from every aspect of spray foam. Too many considerations and too few homes to judge. Building Science Corporation | Consulting & Architecture has many articles on the topic. Humidity control is very important.

Some new schools of thought nix spraying the rafters and instead spray an inch or two on the horizontal ceiling then adding standard insulation. I think Building Science Corporation | Consulting & Architecture has a discussion on this.
Reply With Quote
  #6  
Old 12/4/17, 2:45 AM
Dan Bowers, CMI, ACI's Avatar
Dan Bowers, CMI, ACI Dan Bowers, CMI, ACI is online now
Certified Master Inspector
 
Join Date: Oct 2003
Location: Shawnee Mission, KS
Posts: 9,852
Default Re: AC condenser size and foam insulation

Did a 2-story 2,500sf / 130 yr old house last week with a 2.5 ton A/C and 76,000 btuh furnace. Attic was totally covered with spray on foam insulation.

Only the edges of rafters or joists were visible .... Roof decking was not visible.
Could not see roof vent penetrations inside ALTHOUGH they were visible outside. It took me all of 3 minutes to decide to DISCLAIM & DEFER it out in the report.



Dan Bowers, CMI
Licensed Contractor / Builder
Certified IAQ2 Mold Inspector
Licensed HVAC Service Technician
EDI Certified Stucco / EIFS Inspector
Certified Commercial Building Inspector
iNACHI – US Member of the Year 2010
ITC / FLIR - Level I Infrared Thermographer
FHA - 203k Inspector / Compliance Inspector
ICC Code Inspector (Plmbg, Elec, Mech, Bldg)
Reply With Quote
Reply

Thread Tools

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off


All times are GMT -4. The time now is 8:30 AM.
no new posts