I am new to this forum. I am looking at using SIP's as a construction method for a new house. In talking with a dealer at a local home-building show; his statement about fiberglass was that it was a good filtering agent for air.  However, it does help remove humidity in the air.

If houses are sealed so well is there a potential of having condensation on either the inside or outside of SIP walls? If it does occur, does it occur more with PUR or EPS?  Is there a good countermeasure?

 If this subject has already been beat to death, I'm sorry. As I said, I'm new to the forum.

Larry,

we are used to beating things to death , welcome to the forum!

a filter lets air flow thru which is not what you want for energy efficiency.

PU or EPS makes no difference as far as tightness, the best bet is to build as tight as possible and control the point of freshair intake. You need to contol high humidity to avoid condensation that will form on your windows first.
The countermeasure will depend on your climate, the cure will vary for different parts of the country

My favorite explanation is that the sips home compared to a stick built home is like a brand new Honda as apposed to an old volkswagon. If you roll up the windows on the honda and don't condition the air the windows will fog up right away. Same with the tighter shell of the sips home. You have to do your title 24 calculations for R-35 or higher to figure out the size of the HVAC system you need which will be quite a bit smaller. Then plumb in an Air to Air exchanger. (some call it a heat exchanger) in line with your HVAC unit. They cost around $800-$1100 but you will save a few thousand by downsizing you HVAC unit to the right size for a more efficient building envelope.

Larry,

We also highly recommend adding mechanical ventilation to your HVAC system when building with SIPs. It is important for a structure to breath, but I would much rather have you control the ventilation than your house! Plus K is correct that too often the HVAC units are over-sized for SIP construction, so downsizing units will save some money to help make up for the cost of the air exchanger.

Joe Quinn
[email protected]
www.enercept.com

Larry - One of the benefits of SIPs is the extream comtrol of unwanted air infiltration, or air leaks through cracks, holes and voids. A quality SIPs house should blower-door test down to about 0.1 ACH (1/10 of the inside air leaking out in an hour) We need fresh air, and the potential humidty needs to be vented. An ERV or HRV coupled to the HVAC system is manditory is SIPs houses. These units bring in fresh air while venting stale interior air but RECOVER about 80% of the energy of the interior conditioned air. Roel Cole, Sun Styles Timber Framing, Inc. 804-378-0501