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Insulation around windows - how tight?

Posted by ajsmama (My Page) on
Tue, Mar 10, 09 at 10:47

DH and I were talking about making our 2-yr old house more energy efficient last night, he was saying there wasn't much more we could do "B/c I packed as much insulation as I could around the windows." (while I had the casing off to stain - all the woodwork in our modular came tacked in place loosely). Sure enough, I checked the windows that hadn't had casing put up yet and insulation was packed in pretty much as tight as it could go (maybe gave 3/4" in 2x6 walls when I poked my finger in). I tried explaining that fiberglas insulation was like bubblewrap, if you smash it flat so there's no air it doesn't work as well as if you leave bubbles. Now he's mad at me and says I can pull it all out and redo it b/c he's not doing any more around "my" house. I have 2 ?s

1. How tightly/loosely should insulation be installed around windows/door jambs?

2. Should I pull the casings off the 9 upstairs windows I just paid a carpenter to biscuit join and install (tightly with a nail gun) in order to loosen up the insulation, or should I wait and pay $75 for an energy audit (we were talking about last night) from the electric company to see how bad they are before we rip all that work out and redo it?

Thanks


Follow-Up Postings:

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RE: Insulation around windows - how tight?

You could go for the energy audit, but if you decide to pull the casings/trims, low expanding foam geared for doors/windows works better than stuffing in tight fiberglass which, as you mentioned, renders it pretty much useless. The cans of low expanding foam are available at any supply outfit, hardware store, big box stores, etc.


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RE: Insulation around windows - how tight?

While "loose" would have been better I'd certainly leave it alone. It's probably fine. If it's still cold where you are, put your hand on the trim and feel if there are any particularly cold spots that need to be addressed.


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RE: Insulation around windows - how tight?

The purpose of filling the gap at window jambs is primarily to stop air infiltration. It is such a small area of wall that the insulation effect is of little importance to the heat loss of the house. In my opinion, it's not worth the effort to change it.


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RE: Insulation around windows - how tight?

We were thinking about the energy audit anyway, just to see (were wondering about joints between top and bottom floors) how good/bad it was. Used to be free but now it's $75. DH used Great Stuff around sill plates in basement and put fiberglas batts b/t joists down there before we even moved in. So I figured he knew not to pack it tight. He wanted to use Great Stuff around windows and doors last year b/c could feel drafts (much of the casing though not all had been pulled off to stain as soon as we moved in, though only baseboards had been pulled off to paint/install flooring b4 we moved in). I said no b/c factory rep who came to fix drywall cracks (see my post on Manufactured Homes) said it would push the jambs in. So he went for loose fiberglas (but packed it in, I'm being generous when I say 3/4" give, in some places it's more like 1/2" and that may even be generous).

But thanks for the advice - I won't worry too much about it if it's just to block the air. I was thinking of running a bead of caulk behind the casing b4 installing (don't want to caulk after b/c casing is stained not painted) but DH thought that would be too much of a mess. Now that I have 9 windows with nice tight mitre joints I hate to pull the casings off and mess them up (even if I don't split them, they'd still look like chicken pox after being nailed up 3 times!). I'll just try to pull out all the insulation (original got compressed too) from my uncased openings and put new stuff or low-expanding foam in. I'll check tonight after the temp drops to see if I feel cold spots around the finished windows.

We have geothermal heat with electric backup and we just used 77 kWh/day this past month (avg temp 29 same as last year according to my bill). Last year it was 74. I am on GW a lot more now with old computer running, but not sure why we're using so much (more this year!) electricity. Think an energy audit is worth it? We have Energy Star (though LG claimed it was better than it really is) fridge and DW. Hot water is electric, though it's prewarmed by the heat pump that's not saying much this time of year. Usage is around 40 kWh/day during the non-heating season (even in the cooling season our heat pump is pretty efficient, bill doesn't change much from May - Oct, jumps in Nov when we turn on the breaker for backup heat).

The only other things we could think of were to replace our 3-yr old non-Energy Star washer and dryer (electric) with front-load washer and a clothes line, and to maybe put foam gaskets on the outlets. Don't want to make the house too tight though - we haven't tested for radon, but sometimes we get sewer smell from Studor valve in attic and somehow from basement (along untrimmed sides of stair stringer). So we know we are sucking air from unfinished sections of the house (open soffits, ridge vent in attic) b/c the rest of the house is so tight. Any suggestions?


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RE: Insulation around windows - how tight?

not sure if i am missing something here.... So, here goes:

1. never use fiberglas batt type insulation where there is not already an airtight barrier.
2. Fiberglas does not stop moving air from continuing to move.
3. Outdoor air moves into cracks and gaps in exterior walls, and keeps moving, into the wall, and into the interior, through outlet holes and baseboards.
4. Fiberglas then acts a little bit like an air filter, and it picks up dirt, and turns gray or black after many years. This is one sure way to spot air leaks in the house wrap / vapor barrier, in older houses.
5. However, it is an unhealthy "air filter" as it releases particles of fibreglas all the time.

So,
6. Use something to seal air leaks first, or
7. Use expanding foam, to make an airtight seal that is also an insulator.

Did I hit the nail on the head?

HTH
-david


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RE: Insulation around windows - how tight?

OK David, so not worth it to pull out all the (original and added) fiberglas from around the windows we have cased, but you think I should pull it out and replace it with low-expanding foam around the unfinished openings?


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RE: Insulation around windows - how tight?

Whatever you do it will have no effect on your energy use.


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RE: Insulation around windows - how tight?

If you use Great Stuff around windows and doors, you need to use the Great Stuff Window & Door sealant. It won't bow out the window or door as the regular Great Stuff will.


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RE: Insulation around windows - how tight?

these foams are great for two things. One is making things airtight. The other is insulation.

1. Airtightness is like a plastic bag that has no leaks.
2. Insulation is the trapped air in foam, or bubble wrap or fluffy stuff. This insulates against _conductive_ heat transfer, not radiant. Thicker is better.
Fluffy fiberglas only insulates if there is an air barrier, a house wrap, a sealed environment. Letting cold air slide through is no good.
No matter how much you compress it, you will never be able to turn it into an airtight-barrier.

-david


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RE: Insulation around windows - how tight?

OK. So, back to ? number 2 - should I pull off the casings we have up (probably wrecking them in the process) to put foam instead of packed fiberglas? Or just leave it but do the remainder with foam?


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oh BTW

Doesn't house wrap (plastic) count as the air barrier? DH says he could feel drafts from underinsulated jambs, does that mean the sheathing/wrap was ended on the outside about where the drywall was ended on the inside? Should we get that energy audit done?


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RE: Insulation around windows - how tight?

An energy audit will be a waste or your time and your money.

Up to 40% of the energy loss/energy gain in a structure comes from air infiltration and exfiltration.

Sealing drafts with caulking can be the cheapest and most effective way of increasing the energy efficiency of your home.

Caulk around window and door casings.

Seal penetrations between unheated basements and conditioned space above and unheated attics and conditioned spaces below.

Seal around wires, cables, ducts, pipes, chases, pull-down stairs and access doors, and all other penetrations between floors.

Doing so can increase your home's energy efficiency many times over for pennies on the dollar.

Paying an energy auditor to tell you the same thing is money out the window.


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RE: Insulation around windows - how tight?

Question is how to find all the leaks. Incense stick around doors & windows, DH has already sealed pipe and sire penetrations in basement with Good Stuff. HVAC people taped duct seams and wrapped them (with foil tape). I did notice today standing on the counter that modular company sealed seams in range hood install with plain old duct tape, plus I can feel air coming down onto cooktop. Not sure how to fix that. Shouldn't there be a flapper on the vent so it only opens when fan is on?

We can seal penetrations (vent stacks) in attic with Good Stuff - only other penetration is ductwork coming through chase but I think that's pretty tight. Bathroom fans have firecaulk around them and are under the insulated plywood floor in attic. Have radon pipe running basement to attic (for future use) but it's within exterior wall, should have been glued at joints when house was set I can't get at it now. Walk up attic with solid pine door into computer room - walls are insulated, door is pretty tight to carpet but I can install sweep (don't notice draft).

The auditor is actually supposed to do caulking - I can check again. If they do more than just give list of recommendations it could be worth $75. How about my idea of caulking the back of casing just before installing it? I don't want to caulk around outside of stained woodwork. Or will the low-expanding foam do just as well?

What do do b/t floors? I'm not sure about air infiltration, I guess I can check if leaks around my recessed lights in kitchen. I know there's no insulation b/t floors. But what to do about anything now???


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RE: Insulation around windows - how tight?

without being there, without seeing it, i can't say ....

You are on the right track now because all your questions are about stopping air infiltration and exfiltration. Also, you will now use other products and methods than fiberglas to block air. Your methods to ensure Sealing will get better and better.

Sensing drafts is good for spotting cold air coming in. Otherwise, whether or not you can feel a draft is not a good indicator of air moving especially if warm air is moving out, like in an attic. Stay in the attic for a while with the door closed and you may feel the warm air coming in.

-david


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RE: Insulation around windows - how tight?

OK David but back to question 2 - do I pull off the casings I just had joined up pretty and wreck them just to put foam in instead of fiberglas? Or should I leave those 9 windows alone as homebound and mightyanvil said?


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RE: Insulation around windows - how tight?

you decide, ajsmama. Knowing that the fiberglas is useless. Sleep well regardless of that.

i can't comment because i am not there, and if i were there i might see a hundred other things to do and have a hundred good reasons to do some other task to seal the house better. Sealing against air infiltration and air exfiltration in the rest of your house can occupy you for a long time. If cold air from around the windows is what's bothering you most, redo them now.

HTH
-david


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RE: Insulation around windows - how tight?

ajsmama, if you are planning on getting your house "tight". you might want to condsider going to the expense of having a full house fresh air exchanger installed. Indoor air pollution can be worse for your health than what's going on outdoors. You can get your house too "tight", imo.


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RE: Insulation around windows - how tight?

Thanks sierra. We skipped that $2600 option when we had the GSHP installed, I think b/c they said we could add it later and we were on a really tight budget. Definitely will consider it once we get things buttoned up more b/c we will need it.


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RE: Insulation around windows - how tight?

Where I live folks are doing blower tests, where they pull a negative pressure on the house and tell you exactly where the infiltrations are. Doesn't seem to take that long, not sure how much it costs. Might only be useful for finding worst locations of infiltration.


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RE: Insulation around windows - how tight?

HVAC guy was supposed to run blower test and do Manual J calcs but I never saw results. I'll call him tomorrow. Thanks.


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