ᐅ Insulating windows from the outside using insulation wool and panels

Hello,

I have been following this forum for a while and have already received some helpful ideas. Now that I want to ask something myself, I decided to register.

Here is my situation:
I have a roughly 5-meter (16 feet) wide and 2-meter (6.5 feet) high window wall with a patio door leading to the terrace. The previous owner obviously cut costs both on the price of the windows and the installation, so when walking up the stairs along this window wall, you can clearly feel cold air coming in. The same applies to another single patio door in a different room. Since our gas bill is already quite high and we don’t really need these windows for daylight, I want to temporarily seal off the entire wide window wall except for the patio door, and also completely close the patio door in the other room. However, this should only be a temporary solution to keep out the winter cold. In a few years, we will receive a larger sum of money and then renew both the uninsulated facade and all the windows. Until then, I want to seal these windows as economically as possible.

My first idea was simply to put insulation wool inside on the windows and then cover it with drywall or panels. But I am concerned that moisture might accumulate there. Then I thought about doing it from the outside with insulation wool and panels. No one can see that from outside anyway, and since we rarely use the terrace, it wouldn’t be a problem.

Does anyone have any suggestions or maybe even a better idea on how to temporarily close these openings in a simple and cost-effective way?

Hi, this whole project would have questionable success if your only goal is to reduce heating costs. From a purely economic standpoint, it’s not worthwhile; however, if you have other reasons, you will need to assess it differently (drafts, etc.).

A brief explanation:
Currently, your old windows likely have a maximum U-value of about 2 W/m²K.
Afterwards, with roughly 5 cm (2 inches) of 0.35 mineral wool insulation and cladding, you’d get about 0.34 W/m²K.
That results in a difference of 1.66 W/m²K—considering an area of around 8 m² (86 sq ft), an estimated average temperature difference of 17 K (difference between inside and outside), and a 100-day period, I calculate a savings of approximately 540 kWh. Converted to natural gas, that would be roughly $40. If you can get the wall done for that price, great.
But since a good roll of tape for the vapor barrier costs two-thirds of that, I don’t even need to calculate further...
I wouldn’t do it and would save your time and money for renovation.
A floor-to-ceiling thick curtain will serve the same purpose and can be removed more easily later on.

karliseppel schrieb:

Currently, with the old windows, you’ll probably have a maximum U-value of about 2 W/m²K.
Afterwards, with roughly 5cm (2 inches) of mineral wool insulation at 0.35 and cladding, it will be around 0.34 W/m²K.
That results in a difference of 1.66 W/m²K — with a surface area of about 8m² (86 sq ft), an estimated average temperature difference of 17°K (inside/outside), and a 100-day period, I calculate an energy saving of around 540 kWh — converted to city gas, that would be roughly 40€.

Well, the calculation is quite sobering. The thing is, this window front is on the upper floor, and when you go up the stairs, you really feel like a kind of waterfall, but of cold air rushing down. So my concern is that it’s not just the poor window, but also that it might be improperly sealed. Or would you get that sensation simply because the air inside cools down near the large window front, then sinks, so it’s not actually outside air?

karliseppel schrieb:

If someone can build the wall for that price — great 🙂
But since a decent roll of tape for the vapor barrier costs two-thirds of it,
I don’t even need to do the math...
I wouldn’t do it and would save myself the time and money for the renovation.
A thick, floor-to-ceiling curtain will serve the same purpose and
can easily be removed later.

Working with vapor barriers and so on is definitely beyond my skills. I’ve lived in rented apartments all my life, so have no experience, and I am now trying to learn everything little by little — that’s why I didn’t want to start with interior insulation right away. That’s also why I was thinking about adding insulation from the outside, hoping I wouldn’t need anything more than insulation wool and panels because I already have both (left in the house by the previous owner). I just didn’t want to try it myself and then have something go wrong that I hadn’t foreseen, because I lack experience — so I was hoping someone could also comment on the external option.
You’re definitely right about the interior insulation: I certainly don’t have tape like that in stock.

karliseppel schrieb:

A thick, floor-to-ceiling curtain will serve the same purpose and
can easily be removed later.

I just looked it up, and buying a thick curtain and a suitably strong curtain rod isn’t exactly cheap. 🙁 Does anyone have suggestions on where I could get those cheaper?