Savings will vary by climate. All these systems reduce air leakage rates, with the added bonus that ICF homes add thermal mass.
Systems that locate the HVAC system within conditioned space will also yield improved performance based on the additional volume of the conditioned space and the typical duct leakage rates in your area. For example, if duct leakage rates are 5% (Oklahoma), in 18ft high attics, the additional volume of conditioned space negates the savings by preventing duct leakage to the outdoors. However, a 5-ft attic peak and 35% duct leakage will definitely be worth it.
The way to evaluate these systems in terms of energy savings will therefore be based on air leakage rates for typical stick-framed homes in your area, and the air leakage rate for whatever system you are looking at. Talk to the manufacturers - they should have typical blower door test results.
Cold climate air leakage rates range from 0.5 - 0.7 ACH for new homes. Warm climate ACH numbers are typically around 0.35 because of the reduced stack effect.
Combine the R-Values, ACH numbers, and typical duct leakage rates in a Manual J8 run, and calculate the heating & cooling loads. Remember to take credit for locating ducts within conditioned space. Compare the generated heating & cooling loads in typical stick built homes in your area. Focus on the percent difference between the analyzed system and stick built: these percentages should line up pretty accurately with energy consumption numbers.
The only exception is ICF - thermal mass effects can shift the cooling loads to off peak hours, when electricity costs are lower. You might be able to apply a further 5% savings on top of what Manual J8 calculates.
I am out !!!!!!!!!1
I'm not special.
I just build that way.
Thanks for the reply. I just saw it today. Probably wise to post it on a new thread as the last became a little uncivil.
We have decided to go with ICF again. Cost is not an issue as the bid is the same as stick for a turn-key home. See my post on the original thread I put up today.
We did have some trouble finding a contractor we liked who would do ICF. We found several we liked and agreed to price ICF but we got back stick bids. We finally found one who bid it as we wanted, not as he wanted.
|Powered by Social Strata|