SIPs Thermal Comparison

Has anyone inspected (thermal) a SIP’s built home?

I will be building a custom home for a client who is seriously looking at SIP’s construction, I am curious as to how effective there truly are in comparison to conventional framing with Icyene or my preferred choice, cellulose.


I’ve only seen one built using SIP’s. Expensive home. Lots of crane time to erect it.

There is a SIP section in

Thanks Linus,

You also raised a good point about the crane issue, all the manufacturers are telling me that you can make up your cost in labor time however it seems like much of that is lost in equipment time, not to mention time loss because of crews not continually working with the system.

I like SIP’s in theory but I question the price in comparison to what can be achieved thermally using other systems including conventional framing with the right type of insulation and framing techniques.

I have spent months in developing spreadsheets that tell me my exact cost on various building components based upon current lumber / material prices… I will eventually figure out what SIP’s cost per lineal foot vs some BS square foot price thrown out there. Presently, I can build 2x6 walls 24" o.c. for the same price of a 2x4 wall at 16" o.c., knowing that I suspect using cellulose I can out perform SIP’s when doing a dollar for dollar comparison.

I have already spoken with my HVAC contractor and he has informed me any air tight system which requires him to use ERV’s (energy recovery ventilators) will increase my HVAC cost at least $4000.00

I am surprised that no one here at NACHI has thermally inspected SIP’s to give an independent analysis of the product.

While there is little thermal bridging, I am curious about channels and other openings used for electrical and plumbing.



Find out which HRV/ERV he’s installing. That $4,000 price sounds a bit high for a standard style…but there is a quite expensive (but good) ERV out there.

Its about 4000 sq foot home with high ceiling… I figured that is why.

If you’re going to spend extra to go with SIP, then you shouldn’t need such a large furnace. If the HVAC contractor says that you will add $4k to your HVAC costs, I might be concerned that he doesn’t understand the heating/cooling loads.

In a “Passive House” the only heater is a small unit in the ERV.

BTW, I’m showing that a 9-3/8" SIP has an R-47.6; a 7-3/8" of R-35.7.; 5-5/8" + R-29.4

The best you can get from a 2x6 on 24" centers is about R-18 - unless you offset the studs or add a continuous insulation layer.

Anything more than R-29 is probably not worthwhile in North Carolina.

Here is an idea that might be worth the extra money. Install two layers of drywall. The benefit is not additional R value, but the addition of thermal mass. It takes longer to heat up in the summer day time and longer to cool down in the winter. I don’t know how to model the increased comfort vs. additional costs, but in would be beneficial.



Another problem that will develop with such an efficient, airtight home (both very good things) is that if the design has a large area of south/SE/SW windows, it may overheat. See this brochure from my old gov group: Conserve NS

When you have such efficient homes, funny problems can show up such as overheating. On another thread, I already mentioned one such house in northern Nova Scotia that overheated at family re-union on a sunless late December day with temps below freezing…the heat was from about 30 people at 400-600 btu’s hour and from the kitchen range…they eventually had to open windows!!

From 1985-1992, I was the “troubleshooter” for any real or percieved problems with the New Brunswick R2000 program. One house in my birthplace in northern New Brunswick was having overheating problems in the summer but it was not designed to have any amount of solar gain so as to fit into the neighbourhood house styles.

The house was owned by a couple of practising MD’s. In mid-June, when I arrived at the house, I was met by the housekeeper/nanny…and the house was quite warm. Took a quick stroll through the house as an initial survey, noticing that some stove burners and the oven were being used. After questioning the lady, I determined that much higher use of the stove than is average/normal with today’s busy families was the problem. The family were into having everything from breads, deserts, sauces, meals cooked/baked from scratch…so the stove or some burners were on much of the day.