ᐅ Insulating a cold roof with compressed fiberglass insulation, cost

Dr Hix schrieb:
But do you really have to spend a few thousand euros just to prevent leftover paint from freezing?

I agree with you. I would probably build an insulated chest for the few items that shouldn’t get too cold, rather than insulating the entire storage room. Most of that space upstairs is just enclosed area that’s basically unused and only exists because you want standing height in the attic.

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Nordlys schrieb:
Well, actually I tend to trust a professional on this.

I’m surprised. Your build must have gone exceptionally well for you to still think that way.

This whole thing is nonsense for two reasons:

1) The attic is so cold because the insulated top floor ceiling is blocking your living room heat from reaching it; it won’t suddenly warm up by itself just because you add a few more square meters of insulation wool. Frost protection: none. The only thing that improves is heat protection.

2) You want to wrap your attic completely in foil. Of course that’s possible, but it carries risks as soon as any moisture gets in up there. Normally, water would dry out because the roof space is well ventilated. That possibility disappears if you wrap the roof. Apparently your “professional” also recognizes the risk of moisture getting in, otherwise he could just skip the (additional) vapor barrier and leave the insulation open.

As for the price, it also depends on what you’re getting for it.
In the simplest form, he would screw a batten across behind the knee wall to keep the insulation from falling, tape the vapor barrier visibly onto the roof sheathing, and simply pull it over the knee wall and rafters in the walkable area. Then he would screw a simple layer of drywall panels directly on top—done. And I just read that the price is without taping and finishing.

For this scope of work (which would be sufficient for an attic), I find the asked price somewhat steep. Two people should be able to finish this in two days at the latest. (32 hours at €55 gross = €1760 + materials = about €3500)

However, if he crawls behind the knee wall, installs OSB panels all around on the floor as connecting surfaces, primes everything nicely, carefully fits the vapor barrier around the knee wall, tapes the rafters with nail sealing tape, adds battens to straighten the construction, installs two layers of drywall, and roughly tapes and finishes everything once including corner beads and so on, that would be a very different story.

In summary, here’s the gist:

You want to spend money so that your leftover paint cans can be nice and warm. The “professional” is offering you a basically overpriced solution (why even use drywall panels? You haven’t even laid roof sheathing yet) that does not solve your problem and on top of that significantly increases the risk of building damage. He winks at you confidentially and assures you that you had a great idea—completely without any ulterior motives.

I stick to my opinion: If you’re going to throw money away on something unreasonable, at least make sure you enjoy it.

Hello Karsten, my opinion about the project is also rather negative, and there are two reasons for that:

1) Despite the patio door and the vapor barrier on the bottom, moisture will gradually penetrate, especially every time the door is opened.

2) Regarding your overall approach, the project seems like using a sledgehammer to crack a nut.

If you need more constant (or at least warmer in winter) conditions for certain items, then 11ant’s excellent idea is a much more reasonable solution. Place a chest freezer with an intact seal, but don’t operate it. Inside it stays cooler in summer and warmer in winter, which works well. Or are we talking about storage space of several cubic meters?

Hmm, this requires some more thought before it turns into an order. Give us a moment to consider... I’ll get back to you. Thanks.

My wife and I have put an end to the project today. Now she is spending the money in the garden instead.
She can manage that easily. Karsten

May I join the discussion here? The topic seems to be resolved anyway.

In our case, both the roof and the ceiling between floors are insulated. The quality of the vapor barrier between the upper floor and the roof is average – during the blower door test, it was an issue and was definitely not perfectly fixed afterwards.

The mechanical ventilation with heat recovery system is installed in the attic. Our planner thought this was a good idea, and apparently it’s not completely uncommon. However, in hindsight, I would have done it differently.

How can I identify potential damage and prevent it? Are there threshold values for humidity or similar parameters that I should monitor?

I could easily ventilate the attic through the mechanical ventilation system, but it includes humidity recovery. Would that be effective?