Hello,
Our house was built in 1987. We are now considering replacing the windows. The window installers recommend triple-glazed windows. Thanks to a 20% subsidy, these are actually cheaper than double-glazed windows, which are about 10 to 15% less expensive but not subsidized.
However, a friend, who is a building surveyor, has made us uncertain. He advises choosing double-glazed windows instead. Otherwise, you might risk mold developing in the house. Our wall’s U-value of 0.4 to 0.46 W/m²K (0.07 to 0.08 Btu/h·ft²·°F) is still better insulated than all triple-glazed windows, so the windows tend to be the coldest spot. But the difference would no longer be significant enough to prevent faster mold growth on the walls.
So now I’m wondering if I should play it safe and pay more for “worse” windows. What do you think? Are there any experiences? Has anyone installed triple-glazed windows in a similar house?
Many thanks,
Markus
P.S. Possibly worth mentioning is that we have roller shutter boxes (I believe they are called lintel roller shutter boxes).
Our house was built in 1987. We are now considering replacing the windows. The window installers recommend triple-glazed windows. Thanks to a 20% subsidy, these are actually cheaper than double-glazed windows, which are about 10 to 15% less expensive but not subsidized.
However, a friend, who is a building surveyor, has made us uncertain. He advises choosing double-glazed windows instead. Otherwise, you might risk mold developing in the house. Our wall’s U-value of 0.4 to 0.46 W/m²K (0.07 to 0.08 Btu/h·ft²·°F) is still better insulated than all triple-glazed windows, so the windows tend to be the coldest spot. But the difference would no longer be significant enough to prevent faster mold growth on the walls.
So now I’m wondering if I should play it safe and pay more for “worse” windows. What do you think? Are there any experiences? Has anyone installed triple-glazed windows in a similar house?
Many thanks,
Markus
P.S. Possibly worth mentioning is that we have roller shutter boxes (I believe they are called lintel roller shutter boxes).
N
nordanney16 Feb 2026 18:58[A friend of ours has made us unsure. He is a building expert and says: Better to choose double-glazed windows. Otherwise, you risk getting mold inside the house. Our wall, with a U-value of 0.4 - 0.46 W/m²K, is still better insulated than all triple-glazed windows, so the windows tend to remain the coldest spot. However, the difference is no longer large enough, which means mold could develop on the walls more quickly.
Therefore, I am now wondering whether I should play it safe and pay more for "worse" windows. What do you think? Are there any experiences? Has anyone installed triple-glazed windows in a similar house?]
The choice between double and triple glazing in older buildings is not directly about the number of panes. Mold mostly results from different ventilation—older buildings often have windows installed in a "leaky" manner. With a properly done window replacement, the house becomes just as airtight as a new build.
I would always choose triple glazing if I needed new windows. And to be safe, you should add some additional insulation to the window reveal. For example, remove the old plaster from the reveal and apply a 20mm (0.8 inch) XPS board. You could also use a Wedi board or something similar.
The expert is not wrong, but the reasoning is rather weak.
Therefore, I am now wondering whether I should play it safe and pay more for "worse" windows. What do you think? Are there any experiences? Has anyone installed triple-glazed windows in a similar house?]
The choice between double and triple glazing in older buildings is not directly about the number of panes. Mold mostly results from different ventilation—older buildings often have windows installed in a "leaky" manner. With a properly done window replacement, the house becomes just as airtight as a new build.
I would always choose triple glazing if I needed new windows. And to be safe, you should add some additional insulation to the window reveal. For example, remove the old plaster from the reveal and apply a 20mm (0.8 inch) XPS board. You could also use a Wedi board or something similar.
The expert is not wrong, but the reasoning is rather weak.
G
Gerddieter16 Feb 2026 21:06That’s nonsense – double or triple glazing is just as airtight.
Go for triple glazing; you’re not renovating to old standards – and focus on ventilation:
1. Manual
2. Controlled ventilation – for retrofitting, decentralized systems are usually better
3. Window frame ventilators – then it’s like before, the window is “leaky.” Actually the worst option!
You can try option 1 first, and if that doesn’t work, then go for 2 or 3.
GD
Go for triple glazing; you’re not renovating to old standards – and focus on ventilation:
1. Manual
2. Controlled ventilation – for retrofitting, decentralized systems are usually better
3. Window frame ventilators – then it’s like before, the window is “leaky.” Actually the worst option!
You can try option 1 first, and if that doesn’t work, then go for 2 or 3.
GD
Thank you very much for the responses.
A trickle vent in the window rebate is unlikely to be an option for us, as there is a fairly busy road on at least one side...
I will look into the topic of a ventilation system (costs, feasibility, effort, etc.) so that I won’t be caught off guard if manual ventilation alone does not suffice.
A trickle vent in the window rebate is unlikely to be an option for us, as there is a fairly busy road on at least one side...
I will look into the topic of a ventilation system (costs, feasibility, effort, etc.) so that I won’t be caught off guard if manual ventilation alone does not suffice.
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