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Author	Comments
Chris Poole Posted: May 14, 2008 11:01 AM	Chattanooga area I'm looking for an HVAC contractor in the Chattanooga/North Georgia area that has experience running load calculations/sizing for a new construction home insulated with SPF. I've had a couple of estimates but I don't think they really know what they are talking about. The house is around 3500 sqft with really efficient windows...and a wrap around porch for lots a of shading. One guy calculated 6 tons and a purifier and the other guy said 5 tons with an ERV.
Rob Granger Posted: May 15, 2008 10:23 PM	An ERV has nothing to due with heat/cool load calc. A Spray foam house will be very tight and indoor air quality is important for your health. The EPA requires .278 air changes per hour for a healthy home. The only way you will know if you need an ERV is to have a blower door test performed on your house by a professional. I can guarantee that you will need ventilation of some sort. I would select an ERV. One cannot give any sizing of a boiler/furnace or cooling tonage without square foot wall area, net wall area, Window/door u-ratings, R-value of the wall/roof/attic area, ect. While some HVAC contractors can hit the sizing without any pencil math a lot are not experienced with the high performance of a foam house. I would ask to see his calc in writing, the actual calculations.
Gerry Wagoner Posted: May 17, 2008 09:09 AM	There is a company that specializes in engineering foamed homes. NCFI has the reference. also, an HRV might be slightly better than an ERV in Tennessee. ERV's work better in Arizona etc.. good luck, oG
Terry Shepperd Posted: May 27, 2008 10:59 AM	Try going to dougrye.com. He's big on cellulose but preaches loud about airtight, blower door testing, geothermal, and HVAC. He has a radio show on radio there with some good stuff. Most can be applied to foam even better. But he recomends some good HVAC contractors who know super insulated house load requirements. Way too many build leaky ducts and recommend a bigger units than needed. The best write-up on insulation I have read is David South's "A "R" Fairytale" found at Monolithic.com.

Author

Comments

Chris Poole

Posted: May 14, 2008 11:01 AM

Chattanooga area

I'm looking for an HVAC contractor in the Chattanooga/North Georgia area that has experience running load calculations/sizing for a new construction home insulated with SPF. I've had a couple of estimates but I don't think they really know what they are talking about. The house is around 3500 sqft with really efficient windows...and a wrap around porch for lots a of shading. One guy calculated 6 tons and a purifier and the other guy said 5 tons with an ERV.

Rob Granger

Posted: May 15, 2008 10:23 PM

An ERV has nothing to due with heat/cool load calc. A Spray foam house will be very tight and indoor air quality is important for your health. The EPA requires .278 air changes per hour for a healthy home. The only way you will know if you need an ERV is to have a blower door test performed on your house by a professional. I can guarantee that you will need ventilation of some sort. I would select an ERV. One cannot give any sizing of a boiler/furnace or cooling tonage without square foot wall area, net wall area, Window/door u-ratings, R-value of the wall/roof/attic area, ect. While some HVAC contractors can hit the sizing without any pencil math a lot are not experienced with the high performance of a foam house. I would ask to see his calc in writing, the actual calculations.

Gerry Wagoner

Posted: May 17, 2008 09:09 AM

There is a company that specializes in engineering foamed homes. NCFI has the reference.

also, an HRV might be slightly better than an ERV in Tennessee. ERV's work better in Arizona etc..

good luck,

oG

Terry Shepperd

Posted: May 27, 2008 10:59 AM

Try going to dougrye.com. He's big on cellulose
but preaches loud about airtight, blower door testing, geothermal, and HVAC. He has a radio show on radio there with some good stuff. Most can be applied to foam even better. But he recomends some good HVAC contractors who know super insulated house load requirements. Way too many build leaky ducts and recommend a bigger units than needed. The best write-up on insulation I have read is David South's "A "R" Fairytale" found at Monolithic.com.

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