ᐅ How to Properly Insulate an Older Home?

Hello everyone,

I am currently looking for a single-family home for my partner and me, with a baby on the way.

Over the past few weeks, we have viewed around 30 houses ranging from built in 1860 to 1980. The variety included sandstone, rubble masonry, and brickwork, with many extensions, renovations, and added floors. Some were partially refurbished during the 1970s or 1980s. The windows were made of wood, aluminum, or PVC, roofs included fiber cement (Eternit) sheets, and heating systems ranged from oil, coal, coke, electric, storage heaters, wood gasification, gas condensing boilers to pellet stoves.

Preliminary conclusion: due to the current interest rate situation, the market for houses affordable to us is almost empty. There are only expensive prestigious properties starting at 300,000€ or houses at the lower price range around or below 100,000€, which require significant renovation. The "middle" market mostly consists of heavily overpriced houses that actually belong in one of the other price categories mentioned.

For this reason, it currently seems likely that we will buy a house that is more or less in need of major renovation. In all the houses we have viewed in this price range, the walls, ceilings, and roofs (windows definitely) were uninsulated.

Typically, one only hears of adding insulation from the exterior with polystyrene boards or similar materials.

Since nearly all the houses we have seen also need a complete overhaul of water pipes and electrical wiring, and since I would also like to install network cables and possibly KNX wiring at the same time, here is my idea:

Instead of chasing channels all over the masonry to lay new cables and insulating the exterior walls, would it make more sense to build complete wooden stud walls with insulation wool (stone wool?) on the interior and lay the cables within these walls?

Now my questions:
- Does this idea generally make sense, or is added insulation only effective on the outside?
- Are there special considerations for different types of masonry, e.g., ventilation to prevent mold?
- To what extent does it make sense to insulate (intermediate) ceilings? For example, I would insulate all ceilings that have usually cold rooms above them (bedrooms, corridors, storage rooms, attic).

That’s it for now; I assume further questions will arise.

Thanks in advance for your answers.

Hello,

Insulating interior partition walls is usually done for soundproofing rather than thermal insulation.
The idea of building stud walls/drywall instead of chasing into the existing walls isn’t fundamentally wrong; it can be done. However, the question arises which walls are involved and what exactly you plan to do?
Do you want to remove the old walls and rebuild them as stud walls?
First, you need to consider which walls are load-bearing and which aren’t, so be cautious!
An alternative would be to install a drywall partition in front of the existing interior walls and run the electrical/plumbing lines between the drywall and the original wall.
Whether that makes sense depends on the condition of the house. You need to think that through.
Such drywall construction also costs some money and involves a fair amount of work. Usually, double drywall panels are used for some stability to support shelves, pictures, etc.

Insulating ceilings under bedrooms – some people do it, others don’t. I would consider whether it really makes sense. Bedrooms are usually heated to some extent anyway, so why separate them from the rest of the house?
I can’t say whether that is a useful measure.

Insulating exterior walls... I would generally advise doing all insulation on the outside of the building. Interior insulation reduces your living space, and dealing with vapor barriers and so on is not enjoyable. Exterior insulation is more forgiving, and interior insulation is usually only done if there’s no other option.
By the way, one should always be somewhat skeptical about wall insulation measures and only make a decision after a thorough assessment (possibly with an independent expert) and some calculation.
Personally, I consider wall insulation a task I would tend to postpone in such a large project because I believe the savings are not as high as one might expect.

Roof insulation usually makes sense, but as always, it depends on the condition of the roof. If the house is 50 years old or more, the question often arises whether you need or want to re-roof it. In that case, you can consider whether to insulate from the outside of the roof, from inside, or a combination of both.
Of course, there is also the question of whether to insulate the roof itself or the top floor ceiling.

PS: Since I just completed a similar project myself, I can say it takes an enormous amount of time and effort. Don’t rely on friends to help indefinitely (that’s just a fact).
Also, keep in mind that the costs are significant, even if you do a lot yourself.
I would argue that if you want to renovate/refurbish an old building to the standard of a new build, in the end, it won’t be much cheaper than building new.
The idea of buying a cheap old building and renovating it to be cheaper than new construction is therefore only somewhat true.
When you shortlist houses, be sure to bring an expert to have the property thoroughly inspected. That way, you can better estimate the costs and time required.
If I had not gotten the old building under these conditions, I would have clearly opted for a new build.

Thank you for your detailed response.

“The idea of constructing the walls as timber stud/drywall instead of chasing them is basically not wrong; it can be done. However, the question remains which walls are affected and what exactly you plan to do there?”

Thermal insulation, mainly on the interior side of all exterior walls.

I would not tear down interior walls and rebuild them as timber stud walls but rather add insulation to the walls that separate warm from cold rooms, for example, between the living room and the staircase.

If applicable, a ventilation system with heat recovery could also be installed within the timber stud walls.

I personally bought my house some time ago and renovated almost everything myself, so here are a few tips from a very interested amateur:

If you have to rely entirely on contractors for a renovation, the location and/or size of the lot is (almost) the only reason to buy an older property. And it depends on the state of the technology. Since for you it will be a property under 100,000€ (about $110,000), a comprehensive overhaul is really necessary. This starts with insulation. You should definitely do the top floor ceiling and the roof. Basement ceiling, if there is one, should also be done. I also recommend exterior wall insulation, because it’s not just about saving costs but also about comfort.

Next comes water and electrical systems. Check their condition and renew them if needed. For example, I had a short circuit in the kitchen supply line just one month after finishing the renovation and had to open up a lot of things again. That was a stupid mistake on my part.

Then there is the heating system. Check if the old one is too old. For oil heating, also consider the tank system.

Creating an installation cavity is relatively easy. I glued drywall panels onto the walls in the dining room due to crumbling plaster, which made it easy to run cables there. I advise against interior insulation at first, because it needs to be 100% properly installed to avoid mold.

Well, that was just a brief overview of the work involved. I don’t want to discourage you—I would definitely do such a project again—but it costs an immense amount of nerves. My parents supported me intensively back then, and I don’t think there was a single day when things went exactly as we had planned. I was only 24 and had no background in construction.

And in general, about mold: new windows and a “tight” house require a lot of care when it comes to ventilation. That is the main reason mold keeps recurring.

We have a commercial building from 1979, relatively large, over 450 sqm (4,844 sq ft) in area, upgraded afterwards.
Condition: Built in 1979, asbestos roof, brick veneer, uninsulated air cavity, calcium silicate bricks, wooden windows, oil heating system from 2000, wooden doors.
Approach: Had an assessment done by an energy engineer/energy consultant. Result: no new technology recommended, not cost-effective. Upgrading roof insulation and insulation in the sloping ceilings, leaving the asbestos untouched (not disturbing it prevents health risks), blowing perlite into the cavity, doubling up well-maintained windows with additional strips and installing triple glazing, new sealing profiles, then repainting the windows. Costs: $25,000. Savings: Reduced from 9,000 liters of oil per year to 6,200 liters of oil per year.
Maybe this helps you. Karsten

When do you turn off the heating in spring? At the end of March, I wanted to switch it off because of the warm temperatures, but now it’s cold again, especially in the evening. During the day it’s too warm, but at night the house gets too cold. I have no idea how to best manage this... any tips?