I get asked a lot about insulating old houses, especially in the wintertime. It makes sense. People fall in love with the character rich architecture of these homes, but they don’t want the crazy heating and cooling bills that come along with that character.
Chances are good that if your house was built before the 1960’s, there is little to no insulation. Before the energy crisis of the 1970’s, energy was abundant and cheap in America and it was cheaper to heat your old house than it was to insulate it. Today, things have changed and to save yourself lots of money, it’s a good idea to learn how to insulate an old house without destroying it.
Before you start, check out the EnergyStar website to see what the recommended levels of insulation are for your climate zone.
You have lots of options as far as materials you can use and I won’t go into too much detail about those here. You can read all about the differences, performance, and pricing in my earlier post All About Insulation. For the purpose of this post I’m going to be speaking about blown in cellulose and batts since they are the easiest to retrofit into an old house, but just know that you do have other options.
What’s Your Climate?
Your insulation plans should revolve around your climate. After all, you wouldn’t insulate a house in Miami the same as a house in Michigan. I’ve written two detailed posts about how to properly insulate in either a hot or cold which might be a good place to check after getting the basics in this post. Check them out below.
Insulating the Attic
Before you do anything else, this is where you should begin insulating, especially if you live in the hot southern states. The majority of heat loss and gain occurs in your attic.
The attic is often the easiest place to add insulation. If you have an unfinished and unconditioned attic like many old houses, my first recommendation would be to add batt insulation on the underside of the roof.
Measure the size of the roof rafters. Are they 2×6, 2×8 or bigger? The bigger they are, the thicker the insulation you can fit. You’ll also need to determine the spacing of the rafters. Are they 16″ O.C. (on-center) or 24″? Sometimes they aren’t evenly spaced which means more work trimming your batts to size.
Here’s a quick tutorial on How to install batt insulation.
Once you’ve insulated the the underside of your roof, it makes sense to beef up the insulation even more by blowing in cellulose insulation on the floor of the attic. This will help to keep the living spaces below more comfortable year round. You can rent an insulation hopper from most big box stores to blow in your own insulation with little difficulty.
The trick for blown-in insulation (and any insulation for that matter) is to fill as much as you can without compacting it. Insulation looses its insulating abilities the more it is compacted. It should be installed light and fluffy to work best.
Tip: Be careful not to block any soffit vents with insulation if they are present in your attic.
Insulating the Walls
“How can I insulate the walls of my old house without tearing down the plaster walls?” This is by far the biggest insulating dilemma faced by historic home owners. Can it be done? Yes. Should it be done? That is another question.
Adding insulation to the walls of an old house without any other precautions can result is rotting walls full of mold under certain circumstances. In other cases, drilling holes in the walls or removing a couple courses of clapboard to blow insulation into the stud bays may work with no problems.
The problem is that it is difficult to know which situation you have, and so it’s usually best to leave well enough alone and not insulate the walls. The bigger paybacks are under the floor and in the attic anyway.
Insulating the Floors
If you have a basement or crawl space, the best way to insulate the floors of the living space above is much the same as the attic, by installing batts into the stud bays of floor joists. It will be a slow process in tight crawl spaces, but once it’s finished, you won’t have to do it again and your floors will be much more comfortable year round.
The one tip I’ll give you is that if you are insulating in a crawlspace, make sure you have rodent proofing wire screens installed around any opening to the crawlspace. If you have critters able to access your crawl space, they can make a mess of your newly installed insulation over the years. Rodent proof the crawlspace first, then go about installing the insulation.
I really hope those tips help you to get the job done quickly and easily. You don’t need to go throughout expense and mess of tearing down all your walls just to insulate. That is one of the 5 worst mistakes of historic home owners, but with the information in this post I know you’ll be smart enough to avoid it.
Founder & Senior Editor
I love old houses, working with my hands, and teaching others the excitment of doing it yourself! Everything is teachable if you only give it the chance.