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Replacement Windows vs. Blown In Insulation

Our 1920 clapboard home has numerous large single pane windows. Additionally, the plaster and lath walls are minimally (if at all) insulated. As you might already guess our home is not the most energy efficient at this time. Being young homeowners with a family, we are looking to make energy efficient and cost effective upgrades on a budget. We have received estimates for both new replacement windows and blown in insulation. We need the advise of other "old home" homeowners, to know your opinion on what you consider the most energy efficent changes???? Any advise is appreciated :)

Re: Replacement Windows vs. Blown In Insulation

Both are equally important as far as improving the insulating performance .... however .... installing insulation into the walls and replacing all your windows at the same time would be ideal but expensive to do in one shot. Unless you have won a lottery or have the key to Fort Knox then it's more reasonable to pick one to do first and at a later time budget for upgrading the other.

Having said that here's my opinion.....

The walls would be the first thing to tackle since they cover more surface area and would be the largest point of heat loss in colder seasons and heat gain in the warmer seasons. Also consider improving the attic insulation at the same time.

The windows are another source of heat loss/gain as well as being drafty. The windows can be temporarily improved by caulking / spray foam in a can to seal around the frames . Also you might even carefully remove the interior frames and use the foam between the window frame and the wall structure to stop drafts..... providing there aren't sash weights.

The windows themselves can be covered over with plastic on the inside and a storm window on the exterior during the cold season.
These temporary steps will get you through till you can budget replacing windows .... perhaps doing one room at a time.

Just a thought. :)

Re: Replacement Windows vs. Blown In Insulation

I agree with Canuk. You will likely get more bang for your buck with upgraded insulation. But you can also do some relatively inexpensive upgrades/repairs to your windows to make them more energy efficient. Check out these TOH articles:

Airtight Windows in 9 Steps – Use a weather-stripping kit to make older windows airtight.

Insulating around a window between the rough opening and the frame – see step 8

If you replace the sash weights with spring balances you will not need the weight pockets anymore and you can insulate them.
Replacing Sash Weights with Spring Balances
Insulating Window Weight Pockets

Re: Replacement Windows vs. Blown In Insulation

Change the single pane glass to double pane low-E. Argon gas is better although it costs more.

Also, make sure the windows are all caulked up.

Blown in insulation should not be your first option due to the fact that in old buildings you have diagonal supports in the corners. When the insulation goes in, sometimes half the cavity does not get filled. If expandable foam is applied to the cavity, it could push out the horsehair between the lath and you could end up with lumps on your walls as well as all the holes you will have on the inside or outside which will be an eyesore.

What I would do would be strip the walls down, check the wiring, change if needed. You could add new wiring at this time, cable, outlets etc., apply Batt insulation with the proper R-value and then typical sheetrock or blueboard and then you have a troublefree environment for many years.

Horsehair and lath system will come back to haunt you later.


Re: Replacement Windows vs. Blown In Insulation

I would have say I would go for upgrading the insulation first.
As for diagonal corner bracing i think it maybe more of a regional thing since we don't see much of it around here.
Blown in cellulose is a good option.
The issue about upgrading the wiring might be valid since that age of home would probably still have knob&tube if it hadn't been changed. It would need to be changed before insulating.

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