When we signed the paperwork to have our house designs turned into engineered drawings, we were told it takes about 2 weeks… That was over 2 months ago!

Ever hear the saying, “Pioneers are the ones with the arrows in their back.”?  Being a pioneer can be frustrating.  Hopefully it will also be rewarding at some point.

All kidding aside, the engineers putting their name on these plans are dealing with a first of its kind product.  Engineers external to the SIP manufacturer are used to dealing with wooden studs and are less familiar with the capabilities of SIPs.  We have been trying to understand this, and that a lot of questions or concerns are coming up.  The only option is to give up or for the engineers to work through each one individually – no matter how slowly. So we wait, and I continue to look at the numbers…

I have personally been doing something that most consumers would not (or could not) do.  I have been doing my own heat load calculations for the house.  I’ve come to realize that doing load calculations without a completed building is much like educated guessing.

There are a number of factors that significantly affect the heat loads of a house.  Perhaps one of the most important is air infiltration. Without a structure to test, all we can do is – guess – how the house is going to perform (literally under pressure).  The air tightness of the structure has a tremendous effect on heating loads. To give you a brief idea…

If we use the value of 1 ACH (air changes per hour), our house would require 770 BTUs per hour for every degree F in temperature difference from inside to outside.  If we use the ACH value seen with a SIP house with meticulous attention to air sealing (ACH 0.04), this house would use just 339 BTU/h/F.  With all other things being equal, the tighter house requires over 50% less heat!

Check out http://www.taunton.com/finehomebuilding/how-to/articles/energy-efficient-from-ground-up.aspx to see the SIP house that achieved ACH 0.04.

So, what value do we use?  I’ve posed the question to the experts at GDS Associates (http://www.gdsassociates.com/).  They are going to be doing the Energy Star certification of our house.  They have tested other SIP houses and provided me with a good average number of 0.15 for use in my own calculations.

One thing this does demonstrate is that one can not be too careful about meticulous air sealing of a home.  SIPs naturally help to reduce uncontrolled air flow, but it will continue to be important that all openings and seams be properly sealed.

The average person knows nothing about heat load calculations for a house.  It is much more likely that they only understand the results of these loads in the form of monthly heating (and possibly cooling) bills.  It is my hope that this house will be one of the most energy efficient houses in the world.  Provided we are successful, others should be able to easily replicate (or even improve upon) what we are doing here.  It is my intention to make it so.

Ed