Developer says: No more insulation!

Hello,

I am in negotiations with a developer for the construction of a single-family house and am currently having a discussion about the thermal insulation of the house walls and windows.

The developer offers:
Double glazing, U-value of the window elements (overall) = 1.3
Walls: 15 cm sand-lime brick, 12 cm ETICS 035 plus exterior plaster
The energy certificate specifies a final energy demand of 73.1 kWh/(m2*a), of which 61.6 kWh are intended for heating.

I actually wanted a better insulated house, but the developer strongly advised against it (although I am willing to pay if the extra costs are within a realistic range).
I asked about triple glazing instead of double glazing and an ETICS of 18 cm instead of 12 cm.

The developer’s arguments are as follows:

1. With a wall insulated with 16 cm ETICS, the insulation is so good that moisture on the north side of the building may no longer dry out well, and algae could form on the plaster. Even for facade maintenance alone, a certain “thermal transmittance” would be useful.
2. The indoor climate is also critical in a house that is too well insulated without a ventilation system; too much moisture accumulates, leading to the risk of mold growth and an unpleasant living climate.
3. Regarding triple glazing, he pointed out that in winter, less sunlight would enter the house with a triple-glazed window and thus not contribute to heating the building. In addition, I would lower the shutters at night, which would further reduce heat loss.
4. He reports problems with the hinges due to the heavy window elements (floor-to-ceiling and triple-glazed), which would need to be readjusted constantly.
5. As a conclusion, he told me to forgo better insulation because the additional costs would not be recouped.

I am now completely confused. When I ask the energy consultant at the consumer advice center, they throw their hands up. Apparently, the topic of thermal insulation is quite ideologically charged, and it is difficult for me to calculate the added value of better insulation.

I will make a simple attempt:

121 m2 of living space x 61.6 kWh p.a. = 7453 kWh p.a. = approx. 737 m3 natural gas = approx. €516 heating costs per year
If I lose 25% of that through the windows, the annual heating loss through the windows is €130.
If I can reduce these losses by 20% with triple glazing, the annual savings from better windows would be €25 p.a.
If I compare this to the additional investment cost of about €3000, it only pays off after 100 years. Or am I making a complete logical error here?!

I am grateful for any help!!

Ralf

Hello,
have you already signed the contract?
If not, I would quickly kick the developer off the property......

Don’t let your thoughts of investing more money into better thermal insulation deter you. What the developer tells you is really absolute nonsense.

Even for facade maintenance alone, a certain "thermal transmittance" would be sensible.

meaning that we would have to heat for the maintenance of our facade

2. The living climate is also critical in a house that is too well insulated without a ventilation system; too much moisture accumulates, risk of mold growth and unpleasant living climate.

Of course, you have to ventilate consistently if you wrap your house tightly, but you would have to do that even with 12cm ETICS. Where should the difference be (I mean, ventilation-wise)? It’s about the airtightness of the building.

3. Regarding the triple glazing, he raised the concern that in winter less sun would enter the house through a triple-glazed window and thus may not contribute to warming the building.

That is negligible!!

If you are building new now, it is important to wrap your house as warmly as possible, and then size your heating system accordingly. Energy prices will keep rising and the few extra centimeters of insulation will pay off quickly. The facade installer does not care whether he has to glue and pin 12cm or 18cm of insulation. The price difference is only in the material.

Best regards

Hello,

I calculated the matter purely from an economic perspective on the site "WWW.u-wert.net" and was somewhat surprised.

I have to smile a bit at how it is possible to perform an economic efficiency calculation with "u-value". If it were that easy, I could hang up my profession.
A real economic efficiency assessment requires a bit more!
Better insulation (lower heating loads) enables, for example, significant savings in investments in building services engineering.
The attempt to "smooth out" a high demand due to insufficient insulation through a "beautified" energy saving ordinance proof has backfired on many builders after the fact. I deal with this almost daily.
Nothing against "hobby calculators or planners," but I would base a significant investment decision on a solid foundation!

Best regards

Hello,


2. The indoor climate is also critical in a house that is too well insulated without a ventilation system, ....
3. Regarding the triple glazing, he pointed out that with a window with triple glazing in winter, less sun also enters the house and thus might not contribute to heating the building. Besides, I would close the shutters at night, which would further reduce heat loss.
4. He reports problems with the hinges due to the heavy window elements (floor-to-ceiling and triple glazed), ...

2. In general, a ventilation system is always recommended for such tight houses, which of course also costs money, but better to insulate better and ventilate better than to have higher heating costs, right?

3. That is correct regarding solar heat in winter, but the shutters thing is nonsense; energetically speaking, shutters in most cases are a deterioration because the boxes usually emit more heat than is saved by lowering the shutters. It is rather recommended to have triple glazing plus special thermal pleated blinds.
4. Yes and no, it is clear that triple glazed sashes are heavier, so the frames also have to be designed accordingly. For example, if I have triple glazing and 50-60 mm frames, it’s clear what happens.

Yes, my developer says the same thing. And everything I have found so far in somewhat reliable sources online says the same. If you want better insulation, then for peace of mind, but not for your wallet. I will install an exterior wall with a U-value of 0.3. The extra cost for 0.24 would be 2400 euros. Heating cost savings according to formula calculations: 40-90 euros per year Heating cost savings according to the developer (estimated): 50 euros per year Heating cost savings according to a second construction company (estimated): 50-60 euros per year Take the money to the bank; they pay 100 euros per year for it. PS: I think a great quality feature of a developer is if they have a sense of what is worthwhile and what isn't and b) pass that on to the customer and don't try to sell you all kinds of unnecessary things.

I will install an exterior wall with a U-value of 0.3 at my place.

With which construction do you get such a poor U-value? Which planner does something like that?

What about the other components (roof, base plate, windows), do they have similar U-values?
And you compensate for the losses with a super-efficient heating system (which of course costs nothing)?

I strongly doubt that you comply with the requirements of the Energy Saving Ordinance, but your developer must have calculated it cheaply for you.