Foundation Insulation

[msmity29]

We are having a 2-story new home built in the far west burbs of Chicago. As they prepare to break ground this week, does anyone have any tips on what to looks for? Also, does anyone have any advice on things we can do that the builder might not to make our home more energy efficient? We already spoke to the builder and he will let us do extras ourselves during the construction process.
I have had somone tell me that I should apply 1 1/2" or 2" polystyrene to the outside of the foundation before the builder back fills. Does this sound like a good idea? Where could I buy such polystyrene and any tips on how to install? Thanks in advance!

[tooltroll]

The 'polystyrene' they're talking about is extruded polystyrene foam, available at any home center. One of the most popular (and common) trade names is 'Styrofoam SM'... the blue stuff... and yes, a couple of inches on the foundation will make for a nice snug, cozy basement. If it's not a full basement, but a crawl space, it's still a good idea: It's easier to insulate the foundation walls than the first floor, and the warm crawl space will make your floor warmer underfoot. Note that the foundation wall can be insulated on either side, or (my personal preference) both. It's quite common on 'finished' basements to have 2" of foam on the outside and an insulated studded wall on the inside. Be aware of the difference between 'extruded' foam, and 'expanded' foam: The extruded type is denser, has a higher R value, but is the more expensive of the two. The expanded stuff is only good for doghouses, IMHO. (Okay, maybe birdhouses, too :D )

For optimal energy efficiency, a few details should be addressed:

Most importantly, talk to your contractor. Hopefully, he's one of the good ones. A good contractor understands that 'minimum code requirements' are just that: minimum. The code primarily provides safety: Ensuring the structure is strong enough, that the wiring won't catch fire or electrocute you in the tub, the plumbing won't fill the basement (or bathroom) with toxic sludge, etc. (Also, the code is enforced by humans, prone to error, incompetence and sometimes downright corruption. I've seen many jobs that should have never passed inspection, from the foundation up. When you have an inspector that doesn't care, and a contractor who's only interested in his bottom line, then you have problems. Even some newer developments, built by big production contractors who are supposedly 'reputable,' have glaring defects.) A good contractor will meet minimum code requirements as a matter of course: They have enough experience to know what the inspector is (or should be) looking for, and care about the quality of their work. A good contractor will also be more than happy to overbuild as much as you are willing to pay for, and honest enough to tell you when enough is enough and not waste your money. Bear in mind, though, that everything above the standards of your existing contract will cost extra: there's extra material and labour involved that the you can't justly expect the contractor to cover. You can either rely on written change orders, or renegotiate your contract. In your case, since you're doing the extras yourselves, this might not apply, except in that case of materials you might get through the contractor, who can probably get a better price.

Seal the house as tightly as possible: even the tiniest hairline cracks can add up to leaving a window wide open all year round. Note that, in a heating climate, the seal must be on the warm side of the walls. Warm air carries moisture than condenses in the walls during the winter, if it's allowed to escape. (This will drastically reduce the R value of the insulation, and eventually rot the wall out.) Use the best vapour barrier available, generally 'cross laminated' poly, (which won't rip if a corner of drywall gets poked into it, for instance) and seal it at all joints with the proper tape (Here in Canada, it's the red 'Tuck' tape) and to the bottom sills with acoustical sealant. Use sill gaskets, (a foamy thing that goes between the floor and the bottom sill) and sealer boxes around all electrical boxes. Fill any cracks, especially around windows and doors, with spray foam: good window and door installations should intentionally have about 1/2" cracks all around them for just this purpose, since it provides the best seal between the vapour barrier and the window or door frame. Also ensure that the vapour barrier (inside) and the housewrap (outside) are properly overlapped at all openings. Of course, good windows and doors with good insulation and weatherstripping are a must. You want the envelope of the house as airtight as possible. Keep in mind that the tighter the seal, the more important it is to ventilate the house. This seems like an oxymoron, but the idea is to ventilate the house through an air-to-air heat exchanger that exhausts stale air, transferring most of it's heat to incoming fresh air. Then you have control over the ventilation, so it's not just random draughts through random cracks and holes.

Generally, the more R value of insulation you can pack into/onto the walls, the better. I prefer 2x6 construction with the cavities filled with fibreglass, or better yet, spray foam (not the stuff in the can, the stuff sprayed on with a gun,) and 2" of extruded foam on the outside, under the housewrap. Sprayed foam has very good R value, and is it's own vapour barrier, since it's impervious to moisture. The extra expense of the spray foam is offset by not requiring a poly vapor barrier (and the labour to install it.) The 2" foam on the outside insulates the studs: 10%-15% of the wall is wood that goes all the way through, with a low R value. Imagine all the studs, etc. in a wall pushed all to one end: that's how much of the wall is solid wood. This is also an extra layer of insurance in case some small voids are left in the cavity insulation. Needless to say, you want to avoid leaving any voids, but feces do sometimes occur. All this applies doubly for the roof and/or ceilings. If you include a layer of foam on the roof, you must allow an air space between the insulation and the deck above (that the shingles are nailed to- you can't nail them to or through foam,) usually by supporting the deck off the foam with 1x2's on the flat for a 3/4" space, and the space must be vented at the soffit and the ridge. Otherwise, you'll have ice-damming problems and a leaky roof.

High efficiency appliances will save you tons of money in the long run. Consider an on-demand water heater: water is only heated when it's needed, so you're not paying to keep 40 gallons of water hot 24/7.

The bottom line is: you get what you pay for. Using good quality materials, appliances, fixtures, methods and workmanship will pay off in spades. What's a few extra thousand to protect your investment of many tens or hundreds of thousands, especially since you'll recover the extra expense several times over the life of the house. Seal it up tight, insulate as thoroughly as humanly possible, and spend the extra few bucks to get good quality systems. It's all in the details!

I see I've written a novel here, so let's hope the ending is traditional:

. . . and they lived happily ever after.

[msmity29]

Thanks for all the info! It was very helpful! Unfortunately, after speaking to the builder, he will not let us insulate the exterior foundation ourselves. I can understand this as it could cause liability issues. I am in the process of seeing how much the builder would charge us to do it for us.

As the house now stands, we have upgraded to 2x6 walls with R-19 fiberglass insulation. The builder uses Menards brand Ty-Vek house wrap but no extruded foam on the outside. How important is this? He uses R-38 in the attic and Crestline R-4 value vinyl windows.

Let me know if you have further advice for us. Everything at this point is greatly appreciated! Thanks again!

[tooltroll]

The foam on the outside is optional, but will add R5 per inch: 2" of foam on top of your R19 wall will boost it to R29, and prevent telegraphing of the studs. 'Telegraphing' is where the walls get darkish stripes over the studs on the interior walls: it's caused by vapor in the air condensing on the wall where the studs conduct heat directly outside. Dust particles stick to the moist areas and build up over time.
I'm a bit leery of 'value' anything . . . As stated in another thread, I think you should consider an upgrade.