How to improve existing insulation

mjlbMarch 4, 2009

Our exterior walls are very cold to the touch -- even after adding insulation behind wall outlets. When I redid my bathroom, I saw pink fiberglass insulation in the exterior wall, so I think we must have it everywhere. Our house is about 30 years old; we've had no water issues, and no reason to think the fiberglass insulation has been somehow damaged. But clearly it isn't doing the job any more.

The only thought I had was to open up interior walls and redo, but that just seems like such a waste. Our exterior siding is in great shape, so it seems pulling that off to add insulation would also be a shame. Any thoughts?

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First, you live in a cold climate, so just because the walls feel cold doesn't mean you don't have insulation or that it's ineffective.

Second, you may not have it everywhere. Many people add insulation as they remodel, and seeing it in one area is no guarantee of anything.

Third, fiberglass insulation does not lose ability to insulate with time, so the idea of removing it because it is somehow no longer effective should not be a consideration. (You also may have some insulation, but not all that could be put into the wall spaces, but that can be fixed.)

You need an insulation contractor to come out and investigate what your situation is. If you do actually need insulation, or more insulation, there are several kinds that can be blown inside the walls without a major demolition. This is usually done by drilling 2" holes on the outside, at the top of the exterior walls, so that there is an opening into every stud space. After the walls are filled with insulation, the holes are sealed with caps. There is no need to tear off siding or remove sheetrock.

    Bookmark   March 4, 2009 at 9:38PM
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I guarantee an insulation contractor will have one cure: more of whatever insulation he's selling.

Instead, you might want to consult an accredited energy consultant who can give you impartial advice on how best to wring out more energy efficiency for your buck.

Energy audits will soon be mandatory here for homesellers.

    Bookmark   March 5, 2009 at 1:08PM
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You make a good point. An insulation contractor is ok if they're honest and dealing with a knowledgeable homeowner. But an energy auditor, if one is available, is a better choice, especially since they can point out other things to be done, like weatherstripping, etc. I was thinking of saving the original poster some money with a free assessment, but your suggestion may have a much bigger overall economic benefit, and the advice will not have a hidden agenda.

I also looked at your link on mandatory energy audits for home sellers, which is a great benefit to a buyer concerned about overall costs of owning a home. Unfortunately, for us, I see that "here" relates to Canada. If the U.S. ever gets on board with this idea, we would -- all-too-predictably -- have many people upset with another government requirement, even if it would save homeowners bundles of money in the long run.

    Bookmark   March 5, 2009 at 1:47PM
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It's been a while since I posted on this topic, but I too am interested in it.

I've got a house in gardening-zone #6 - which is coldish in winter, but not Minnesota or deep-Canada cold. The house is two storey, built in 1976, 2x4 stud-frame, with fiberglass batts in the walls, and 10" of vermiculite above the second-floor ceiling. Siding is an under-layer of plywood, then a sort of board & batten of vertical 1-inch cedar boards. Windows are sealed double-pane, and none on the first floor west or east (and minimal on the north). Full basement, most of which is below grade.

I've done a lot of work sealing up around doors, electrical outlets and light switches. We've got a high-efficiency wood-burning furnace and fireplace insert. We have an electric back-up system, and burn no more than four cords of firewood in a year. But I believe we could do even better.

I'd like to increase the exterior wall R value without having to buy and install new window casings. So I'd like to remove the vertical exterior siding, add a thin (say, 1/4 or 3/8 inch) layer of some super-insulating sheet material, and put the siding back up. I'm a good DIY carpenter, and I've removed and replaced the siding before in places, for attaching a deck and putting in a new door to the south. So I know it can be done without too much trouble.

I've heard rumors that a thin-sheet insulative material has actually been developed. But no one has been able to tell me about it.

Anyone here know?


    Bookmark   March 5, 2009 at 5:48PM
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Geez -- I thought I already followed up, but must not have hit 'submit'. I appreciate the comments.

I am almost certain that we have fiberglass insulation in all of our outside walls. My gut feeling is that the insulation is not butted up tightly against the studs, and that is partly why there are cold areas on the walls. If that is true, is it possible to blow in insulation on top of fiberglass insulation? Is it a bad idea?

We hired a energy auditor (same as one used by 'This Old House') last summer, who unfortunately could find no major problems with our house. But our energy useage increased dramatically (not related to price changes) from the prior year. It's a real mystery as to what changed and why the house now will not hold heat.

    Bookmark   March 5, 2009 at 7:21PM
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Well, fiberglass roll insulation is sized so it fits snugly in a standard stud space. So, unless you have odd-sized stud spaces that are wider than the roll, and there are big gaps in the stud spaces, this is not an explanation. How cold is this winter compared to last year (your utility bills should show degree-days, which is a relative measure you can use to compare from one year to the next)? How much has your energy usage increased? Do you have growing kids who are taking more or longer showers? Do you have any fireplaces with open dampers? How efficient is your furnace and when is the last time it was serviced?

I'm sorry, but I'm still not buying that your insulation has quit working...just not possible.

As for blowing in more insulation, there's no problem with that. But there may not be much room for it if the walls already have fiberglass in them.

    Bookmark   March 5, 2009 at 9:32PM
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Kudzu -- thanks again. It sounds like I should move on to looking at windows and doors, and leave the insulation alone.

It is a mystery. The heat pumps are serviced twice a year, no open dampers on fireplace, no kids. Energy use went up about 30 percent. Energy auditor compared total degree days, which was up some, but not that much. Because we have heat pumps, supplemental electric heat kicks in when it's below about 20 degrees F, I think. Energy auditor theorized that if we had more very cold days, that might be the answer even if total degree days was not that different from prior year.

But regardless of the mystery, I just want to stop the amount of cold air entering house, and warm air leaving the house. Our HVAC service man noted that when the heat is turned down, temperature inside declines about 2 degrees in half an hour -- which apparently is pretty bad.

    Bookmark   March 5, 2009 at 10:52PM
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The other variable is the outdoor temperature. This has been the coldest winter in MA that I can remember in 45 years. You're lucky if you can keep your house at a comfortable temperature whatever the cost.

    Bookmark   March 6, 2009 at 7:59AM
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super-insulating sheet material,

The highest I have come across are foil-faced polyisocyanurate panels, which have a stabilized R value of 7.1-8.7 per inch.

    Bookmark   March 6, 2009 at 8:52AM
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worthy wrote: "super-insulating sheet material, The highest I have come across are foil-faced polyisocyanurate panels, which have a stabilized R value of 7.1-8.7 per inch."

That's pretty impressive. Thanks. I'll do an on-line search of "polyisocyanurate panels" to earn more (brand names, included).

I can't help feeling that something like this could conceivably help mjlb (thread starter on this thread) too. The old 2x4 stud walls with fiberglass insulation may have seemed normal 30 years ago, but they don't stack up anymore.

    Bookmark   March 6, 2009 at 10:47AM
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