eps or epx foam under slab

[Frozen Canuck]

For sure Tom, I always enjoy threads of this sort.

My grandkids should be able to live in what we now consider McMansions +4000 sq/ft & heat the thing with a little 20K btu boiler in the future. We are already close, <10 btu sq/ft is acheivable by many here now & those of us who are really working on it are looking 5 btu sq/ft square in the face now. 1 advance in window tech & we have it. As that is the largest loss.

For them (grandkids) choosing a very high quality heating appliance will be important as with these low consumption/run times the unit is quite likely to last 3 times as long simply because it sits & waits for a call for heat for so much of it's life.

Heck when we can get it down to 5 btu sq/ft here I think the heating industry (may) just switch over to a roof mount solar HW heating system & the fossil boiler will just be there for backup. Most homes have enough roof space to heat a home that only needs those numbers.

Time will tell but we are close already.

 

[BoilerMan]

FC, I enjoy these type of threads very much too! One of the good things the internet has brought us, collective minds and collective discussions from people from all over the world. I'm at 14btu/ft at -45F here, and I bu no means did a whole lot unconventional. Tried and true tech (DOW Tuff-R) and strapping over fiberglass (would use Roxul now). It kills me to hear of people burning 1,000+ gal of fuel and having to make payments year-round to the oil man. Ah well, great thread!

TS

 

[Frozen Canuck]

For sure BM. I have always believed that adding insulation, even poorly done had a better ROI than any heating system. Felt like a voice in the wilderness through the 60's to 90's, not so much anymore. Now lots of folks are getting REAL about saving energy & money. That's good keeps old dogs like me on top of our toes so to speak. Current with new tech.

 

[Floydian]

This was just posted today-seems relevant to some of the discussion in this thread.

http://www.greenbuildingadvisor.com/blogs/dept/musings/all-about-thermal-mass

I am sure some lively debate will follow in the coming days in the "comments" at the bottom of the page. I am curious how the Passivhaus folks will respond as super(duper) insulating+solar gain+thermal mass(how much?) is a important part of achieving the ridiculously low Passivhaus standard of 4.75 kbtu/sq ft/year.

As far as low heat loads,

Here http://www.greenbuildingadvisor.com/blogs/dept/green-building-news/striving-passivhaus-affordability is an example of a Passivhaus that beats the standard by a margin. At 3.1 kbtu/sq ft/yr (heating) for a 1600 sq ft house, that is a whopping 5 MM btus/yr in a 7300 HDD climate. Simple heating systems, very low energy demand for the life of the building and comfort is a given.
Honestly I don't care about some certification, I care about performance and this is about as good as it gets. Now for someone building their own house and committed to burning wood, I think building to Passivhaus standard is overkill. If someone is hiring out the building of a new house and is not interested in the commitment to burning wood, Passivhaus or near passivhaus starts to make a lot of sense.

I really like the "Pretty Good House" approach: http://www.greenbuildingadvisor.com/blogs/dept/guest-blogs/pretty-good-house

Noah

 

[heaterman]

At the energy conference in Austria there were a number of manufacturers with boilers (pellet only) that fired well below 10,000btu. Can you imagine buying only a ton or two for an entire years worth of heat and hot water?

Getting back to the original posters question.........I've used both with good results. The density of the product is the main concern as far as holding up goes. Lately we've been buying an EPS product that has a poly type scrim on one side and an aluminum scrim on the other. Very resistant to moisture because the only area exposed is the edge of the panel. I can even order it with bug killer impressed right in the foam.