Renovate house from 1938/70 various questions

Hello everyone,

I hope I am in the right place with my questions. First of all, I know that no concrete statements can be made based on descriptions or pictures.
First, a few data in advance:
I have a house from 1938 with an extension from 1970, with a total of 200 sqm of pure living space + 100 sqm of basement.
The windows are from 1979 and double-glazed.
The radiators are still 95% ribbed radiators installed in radiator niches.
The gas heating in the basement is about 20-25 years old.
The roof and upper floor ceiling are uninsulated.
The attic will NEVER be converted, so we wanted to reroof the house simply with an underlay membrane and insulate the upper floor ceiling.

Now we are faced with the question of what to do with the windows/facade.

Since I would claim that the facade area is fairly large, the insulation will be correspondingly expensive. Now the question arises for me how many % more savings can be achieved with triple-glazed instead of double-glazed windows and exterior facade insulation? Is there possibly a guideline value?

And is there a guideline value if, compared to the current state, the windows are replaced by double-glazed thermal insulation windows, the upper floor ceiling is insulated, the radiator niches are closed, new radiators and a new heating system installed? I have searched various sites but unfortunately found no direction.

I just want to get a feel for what percentage share one is talking about with such measures.

Good morning,

I am in the final stages of a very similar project. Generally, the first question is whether you want experiences from the group of "Neubauten-Hipster-KFW-Energieeinsparverordnung-gibt-es-eine-DIN-für-richtiges-Lüften" or rather from the DIY in self-management corner. I could provide some information from the DIY corner.

Leave the insulation on the outside alone for now.

In 1995 there was a new thermal protection regulation – after this time, almost exclusively windows with double glazing and insulating gas were installed. Before that, in most cases, windows with double glazing without insulating gas were installed. The big leap in U-value from double glazed with insulating gas to triple glazed with insulating gas is rather small. From the perspective of sound insulation, however, triple glazing makes sense. You can laboriously search for a manufacturer and model designation on a window frame or simply hold a candle in front of your pane to find out if you have windows with insulating gas (just google it – it will then be explained to you). If it is double glazed windows without insulating gas, you could replace them and achieve a significant improvement in the U-value. Whether then double or triple glazing depends on you and your budget.

If I look at your windows, you have your roller shutter boxes inside. Consider insulating the roller shutter boxes from the inside. Small effort with great effect. It doesn’t cost much and you can easily do it yourself.

Under your windows are then the ribbed radiators and the niches. You build up the niches and install newer radiators.

Depending on what your floor plan looks like inside, you should consider replacing the glass blocks at the entrance door downstairs.

With the living area, you can safely leave it as a cold roof and simply insulate the ceiling above yourself. Possibly also insulate the basement ceiling.

If the gas heating still works – keep it.

With these points, you achieve a great effect with minimal financial effort ... of course, you are still far from all the low-energy houses, but one thing at a time.

Then consider, if you want to really renovate properly, what you will do with the water, wastewater pipes, and electricity. The heating pipes are usually indestructible, but just take a look at them. Properly insulating water and heating pipes is again a small effort with great effect.

Thank you for the quick response!
Let me put it this way: of course I want to do and have done a few things with the latest standards (windows, roof, heating), but it doesn't have to go in the direction of a passive house; in my opinion, that would simply be too much for such a house.
We do all the preliminary work and other tasks ourselves as far as possible.

That was also my idea, the old windows should have a 3.0 value, and the new double-glazed windows with thermal insulation glass should have 1.1 and would definitely be an improvement. We hardly have any noise on our side, so that wouldn’t be very important for us.

Exactly that with the roller shutter box I also wanted to tackle in this context while everything is open.

Okay, that sounds good that I am not mistaken about the insulation of the upper floor ceiling. The cellar ceiling will be more difficult since we hardly have any room height there and I don’t want to lose any more space.

Yes, the pipes should be checked and renewed if necessary.

Unfortunately, I have no comparison for the savings; currently, my grandfather still lives in the lower apartment (the apartments are not separated from each other), and we would move into the upper one. When my parents still lived in the house, they had an annual consumption of about 50,000 kWh gas for 200 sqm of living space including my grandfather. That seems very high to me personally. However, they were the type to mostly keep the heating running and the windows tilted.
If I could get down to maybe 30-40,000 kWh through more careful heating and the above-mentioned renovation measures, I think I would already be very satisfied.

Yeah, insulating the top floor ceiling can be done in a weekend and you'll have the costs back in 2-3 years. By far the most effective. If the windows are basically airtight now, new ones won't bring a significant improvement. However, they are quite old, so you can do it, it's quick to do, but it costs money, same for the front door. Keep the heating system and radiators as long as they work. Ribbed radiators are not worse than 'modern' ones. You can insulate niches, I skipped it for aesthetic and practical reasons. If you don't need the space, do it, but work neatly. That means the insulation material must be glued flat and cleanly. If moist, warm air gets behind it to the cold outer wall, you'll have mold in no time.

The question for me would also be: Do you want to renovate solely economically, or is living comfort also important? If exclusively economical, facade insulation must definitely be calculated precisely (please consider that in addition to energy savings, the value of the house also increases in the event of a sale). A huge advantage of insulated exterior walls, however, is "warm" walls, meaning no unpleasant cold radiation; this is already a huge added value of new buildings compared to uninsulated old buildings.

Before you start doing anything, I would definitely find a capable energy consultant in your case to create a coherent overall concept. Individual measures can quickly backfire (typical example: windows insulated too much compared to the rest, water now condenses on the walls because that is now the coldest point --> mold problems).

Do you have more information about when what was done to the house?

We renovated our house built in 1921, but our facade, roof, windows, and doors are from around 1992 and are still completely fine, and we have very low energy costs.

Also inform yourselves about what you are legally obligated to do – in the case of ownership changes, some things become mandatory regarding energy renovation. However, I can’t tell you anything exact off the top of my head right now, for example, we did not insulate our basement ceiling or ground floor (uninsulated basement) (where there’s no complainant, there’s no judge...). Things like ribbed radiators in niches are something I personally think should be renovated, but in the end, everyone has to decide that for themselves. In your case, an energy consultant through [KFW] would certainly be worthwhile, since you will probably finance this (?), and then you will need them anyway for the loan approval. They can also calculate that for you for their money.