Insulating for A/C

[GasSavers_katman]

Don't forget the vapor barrier for the attic. Keep the attic vents open in the winter. Vapors from the house rise and make the insulation wet. Wet insulation is inefficient.
One of the main reasons for insulating the foundation is thermal storage. Keeps the temps much more even.

Wow Boxchain, how much did that run you?

[boxchain]

$1.25-$1.50/sq ft of outside wall area (not house sq ft). I know you can buy fiberglas for $0.50/sf, but you still have to install it (they come out and spray it for you) which is never any fun.

It's an old house (1880s) with no vapor barrier, in order to have one I would have to tear out all of the siding (much of which is still in good shape, old cypress) and replace it. SO the foam also acts as a vapor barrier. And living in New Orleans, I've see what happens to fiberglas when it gets wet :O

Lastly, the foam actually adds structural integrity, something you can't have enough of in a hurricane prone area

They do make foam that you can apply with minimal sheetrock damage, but it's more expensive. The other route you can go is blown cellulose, which my old landlord did in my last apt. It works pretty well, but it tends to settle, so you lose insulation at the top, and rodents love to nest in it.

[8307c4]

It gets better, most homes are severely under-insulated.

Current green standards recommend R-49 ceiling (house-to-attic) and R-30 floor (basement-to-house), and more can be done at the roof level and then of course windows and walls.

I found my ceiling was R-11 and I just this last November DIY project took it to R-20. It was a PITA but the difference I felt immediately, the heat pump ran less and for shorter periods of time, also it takes longer for the house to react to an outdoor temperature change and when heated it stays warm longer.

My floor is also R-11...
As you can see I have work to do, but I have to be in the mood for it because it's royal dealing with these fiberglass rolls.

Other things I noticed:
I keep my thermostat for inside set to 64f, this helps considerably but...

My basement is sealed in the winter months, and tends to stay in the low 50's (52-56f). On a warm day, opening the door to this basement for a period of time of 4-6 hours raises the temperature by about 8 degrees up to just over 60, like 62 or so (we do get some 70 degree days in winter here in VA).
Doing that, several hours later raises the interior temperature of my house by 4-6 degrees.
I found it interesting how it can be 62 in the basement yet raise my temps to 68 inside the house merely via this apparently silly method.
Not opening the basement door in contrast, on a 70 degree day still helps, but not as much.

[Snax]

Originally Posted by Snax

Yup, the ductwork and air handler should ideally be in the conditioned space for best efficiency. Another article in the same magazine suggests that it is far better to have conditioned crawl spaces than unconditioned vented ones, both from an efficiency standpoint, and from the standpoint of keeping moisture accumulation low. As for attics, piling it deep never hurts and is easy to do with loose fill.

In fact, after reading through that issue, I have firmly decided that whomever installed our HVAC system didn't really have or clue or didn't care enough to bother with doing things right. So tommorrow we are having it serviced, admittedly for the first time since we moved in here 5 years ago. (And we suspect is hasn't been touched since it was installed 11 years ago aside from filter changes and when I cleaned the air handler myself and replaced a faulty motor start capacitor.)

Well the good news is that everything is ok with the system except for a motor start capacitor that needs replacing at a cost of about $10 the DIY route. The unofficial opinion from the tech was that it wasn't worth considering any kind of system upgrade unless something major failed.

So I'm just doing the regular stuff myself like placing R-5 foam around the air handler and considering an HRV.

[HHO4ME]

get online (google) and type in radiant barrier insulation. It's called insulation but it actually reflects 90+ % of heat so in a well ventalated attic it works great. Power fans are over rated, phyics can do the job for free

[GasSavers_Ryland]

Originally Posted by HHO4ME

a well ventalated attic it works great. Power fans are over rated, phyics can do the job for free

power vents are ideal if you can't fit enough normal roof vents, like on a hip roof or if you have another weird shape, I've installed them and you can feel them pulling the hot air out of the attic space.

[MiddleMike]

Originally Posted by Tofuball

I know when you insulate for heat, you want to start from the top of the house and go down, and ways to do that include properly insulating the attic, caulking and sealing around recessed lights, vents, etc, and working down from there.

My question is, is insulating for A/C simply the reverse?

You insulate the house as if you are insulating to save energy costs. There is no pre-defined "order of operation" I know of that cannot be hotly contested. Insulate the attic first for heat? Ok, fine, but then you don't seal the basement or insulate it, and that nice cool AC air you paid good money for quickly flows right down into the unsealed and uninsulated basement and seeps into the earth lickety split. Contrary to popular belief, you cannot ignore a basement in your insulating scheme because "earth is a good insulator". It may well be, or not, but once the energy is outside your cinder blocks all you're doing is keeping/retraining the heat/cool outside your house.

Insulating and sealing, ideally, would be attic/walls/basement, at once (or as close to once as you can get). R38 (for temperate zones) and then top it off with a good radiant barrier in the attic. Remember to seal every wire/pipe entry you find in all areas first (there are exceptions of course, chimneys you have to block around and bathroom vent fans you don't cover either), and don't forget to seal the sill plate area where the basement and house pad meet with a good 20 year caulk (highly important). Also ensure you have very good circulation in the attic, that your soffit vents are clear and that your gable/sill vents are open and clear and moving air through convection (or fan if need be). The next best thing to do is to add some kind of shade (artificial or natural) to all windows that are exposed to the sun for any length of time during the day. Exterior shade is far better than interior shade (curtains) since it stops the heat/radiant heat from ever getting in to dissipate.

Ideally you insulate where you can afford to do so, regardless of order of operation. Most folks pick the attic because it's the easiest to get to, then neglect the other areas thinking they've done their job. The energy consumption improves, sure, but not nearly as much as if they'd taken on the whole house holistically as they should have. A well sealed and insulated house with windows shaded to keep out maximum radiant heat can obtain 50% to 70% less average energy consumption than a normal mass production home like most people live in.

See here: http://www.builditsolar.com/Projects...nservation.htm

For more insulation details

[MiddleMike]

Originally Posted by Ryland

power vents are ideal if you can't fit enough normal roof vents, like on a hip roof or if you have another weird shape, I've installed them and you can feel them pulling the hot air out of the attic space.

Power vents are great, but you have to have everything sealed below them for them to be effective. Most folks put one in without Great Stuffing/caulking all air leaks up to the attic, then are baffled as to why their energy bills aren't going down as much as they thought they would.

Create a good airflow with a fan and unsealed holes will suck up AC air into the attic as well as from the soffits.

[MiddleMike]

And also, sealing the ductwork then insulating it, to save on both heat and AC, is a must. That's probably the biggest payback per dollar thing you can do, outside of a full blanket insulation project on the home.