Tips for insulation thin crawling

[dhaulagiri]

Hello,

I come to ask your advice, because I find it difficult to choose the right insulation to renovate the attic of my house.

Location: Gard, altitude 125m, a little in the hinterland. Warm in summer, relatively cold in winter but fairly sheltered from the north wind.

My house: probably the prototype of the 80's thermal colander (1983) but I am trying to gradually remedy it according to my renovation projects. Concrete block construction on uninsulated crawl space. At the walls, 75 mm of glass wool, 50 mm plastered brick, plaster (original) and earth plaster (renovation). At the ceiling level, a concrete slab. For 2/3 of the space in lost roof space: 31cm of projected cellulose wadding (renovation). For the 1/3 in attic space that is the subject of my request, nothing yet. I'll come back to it ... The frame is traditional (25x11cm purlins and 8x6cm rafters) and the cover was completely redone in 2012 with HPV film, ventilation blade and curl. During the roofing work, the original glass wool in the converted attic was very damaged, notably due to rodents, and it was removed. I didn't have the budget to finance this part of the insulation at the time and I can only get down to it now. So it had not been isolated for 4 years.

The attic: they consist of an extra bedroom and a bathroom. It is not used much at the moment, mainly to accommodate family and friends, but my daughter, soon to be a teenager, should move in after the work. The project consists of redoing everything: we break, we isolate, we review the distribution of parts and we redevelop. The floor area is just over 40m2 but only 12m2 will have a ceiling height equal to or greater than 1,80m after work (see below). The flat surface to be treated is approximately 70m2, including two roof sections and two straight feet.

Regarding insulation, my main constraints are:
1) Insulate from the inside
2) Do not exceed 16cm of insulation thickness, because beyond the living space would be too reduced. Let's even say that it would be hard to stand up. With a greater thickness, the part would no longer even be considered as such vis-à-vis the Carrez law. It would be a loss for my house so ...

My wish is to obtain maximum resistance with my famous 16cm. As we are under a roof, I would also like to avoid summer overheating (there is not and there will be no air conditioning at home ...). I would also like to find a product that is as ecological and as inexpensive as possible. Finally, rodents regularly visit the attic and I would like to complicate their task and prevent them from doing significant damage. A little squaring the circle so and I am therefore very annoyed to find MY solution.

For now, my alternative would be as follows for a substantially equivalent price (between € 1300 and € 1600 by doing it myself and not possible to go beyond)
- downgraded polyurethane panels. Advantages: an R of 7,4 with 16cm and probably fairly limited damage with rodents (the two most important points for me). Cons: everything else. Suddenly, I am not very wrapped (but I may become so, well sealed in my plastic shell )
- wood fiber. Disadvantages: an R of 4,2 with 16cm (bof bof), a greater sensitivity (important anyway?) To rodents. Advantages: everything else, even if they are probably reduced by the insufficient thickness, notably the phase shift. So, I tell myself that the investment is not worth it ...

I immediately excluded mineral wool, because of rodents (and also because mineral wool is not good for health and for the planet. Yes, polyurethane either, I know, but everything world has inconsistencies my good lady ...). I cannot effectively protect my roof spaces against their intrusion, that would be too complicated. Given the configuration of the house, they could pass through the ventilated blade under the tiles, through the banks or the shutter (mounted dry). Putting a fence would be very tedious from the inside and certainly ineffective, a mouse can pass through a hole the diameter of a pencil.

There, you know everything! Thank you if you have read everything and, as that may mean that you are interested in the subject, thank you for giving me your informed opinion.

Nicolas

[Did67]

I can't recommend a "reflective screen" under the roof enough.

In summer, at your place, but at my house too, the roof is hot. This is an overhead iron, which "radiates" its heat even on contact. Whoever once worked under a roof, in a barn (stacking hay, etc.) sees what I'm talking about.

You may well have I know not what phenomenal R, the thermal radiation will play. We must not only focus on thermal conductivity, in the attic.

It is always difficult to combine several materials. Nevertheless, at home, I put glass wool then a thin insulation, then paneling, also in very important space constraints (the LoS is slipped between the metal purlins - in addition, I had a roof " radiator "!): development of the roof tip with approximately 2,20 m at the highest point!

Well that remains "average", also because in this arrangement of the tip of my roof, there is no no thermal inertia. Everything is, by nature, made of light materials.

And the combination of "little or no inertia" + "medium insulation" cannot give good results ...

It remains livable ...

[dhaulagiri]

Hello Did,

I'm glad you answered me, because I know your pragmatism and common sense since our endless debates on boilers and their settings a few years ago.

For the reflective screen, this will not be possible: we would have to find out. I should have done it when I redid my cover a few years ago. I then contented myself with adding an HPV screen, because I did not have the means at the time to do more insulation. If I could, I would probably have been sarking. At least, we no longer take water during the Cévennes episodes and that's already a lot!

So I have to go inside with constraints of habitability similar to yours: under the ridge breakdown, I only have 2,02m. A little more once the insulation (assumption 16cm) and the placo installed.

Polyurethane makes me hesitate for the reason you mention (heat accumulated under the roof) even if the one that I am offered (it is the second choice) is a panel covered with an aluminum film, therefore reflective, in principle intended for sarking. Except that I will have to use it under the HPV film: I don't really know what to think about it, especially since I have to put in two crossed layers: so 4 aluminum films (since 1 on each side of the panel). The diverted uses are not always relevant in the field of construction ...

My other problem is the rodents: they had massacred the original glass wool, removed 4 years ago by redoing the cover. So, I hesitate to put them back, because I can't effectively prevent them from entering.

In terms of inertia, I am "lucky" to have a concrete slab between the ground floor and the attic and 5cm hollow brick partitions. It's always better than any plasterboard. On the other hand, obligation to redo the crawling plasterboard (I was given it, so I will not spit on this economy) and I do not see anyway how to make a crawling partition combining lightness and inertia other than sarking, therefore from the outside. That said, I am far from knowing everything and knowing everything on the subject, otherwise I will not ask myself questions today ...

[Did67]

Yes, indeed, your username comes back to me ... I'm thinking about Reinhold Messner. And the discussions on the boilers - mine will soon be celebrating its 10th anniversary ... And it still provides. Particularly at this time, with negative temperatures that sometimes do not become positive during the day.

Now, my passion that occupies me here is more gardening: the "Potager du Laesseux"

agriculture / gardening-more-than-bio-by-plant-live-without-fatigue-t13846.html

I do not understand how you gain in height, when you are going to add insulation ???

When I was talking about radiation shields, I was thinking on the inside, to stretch a "thin insulator". I made a sandwich like:

- glass wool in panels slid and fixed between the metal purlins (spaced 60 / about 20 memory deep).
- crooked slats
- thin stretched insulation
- re-slats targeted on the first
- paneling

But I think that your polystyrene panels if they are covered with an aluminum film will precisely play this role.

Be very careful with condensation in cold corners, whether with these panels or with thin insulation: there is a risk of condensation.

VMC obligatory, or else it will "drip" somewhere!

I don't know if there was a way to do better! As said: no inertia, since my floor is OSB placed on my crosspieces, which are also metallic (my roof frame is a sort of successions of large A's; the layout is in the top triangle; the two legs are the crawlers of the 1st floor). It's far from top, but it's livable. In winter, I have the right radiators ("low temperatures" connected to a bypass of my 1st floor heated floors; oversized). In summer, it is necessary to manage well: Velux window with motorized external roller shutters, which must be closed; open at night ...

[dhaulagiri]

I do not understand how you gain in height, when you are going to add insulation ???

It's very simple: the base of the ridge purl is 2,02m from the ground. But the thickness of this breakdown is 25cm, that of the rafters is 8cm and I will put only 16cm of insulation + BA13. My breakdowns will therefore be apparent from 7 or 8 cm under the plasterboard once the site is finished. It's very simple but I was not clear ...

But I think that your polystyrene panels if they are covered with an aluminum film will precisely play this role.
Be very careful with condensation in cold corners, whether with these panels or with thin insulation: there is a risk of condensation.
VMC obligatory, or else it will "drip" somewhere!

It's polyurethane but whatever, the properties are the same, good or bad. It's just a little more insulating. The problem is that the guy sells me panels for insulation from the outside to insulate from the inside. Each panel has an aluminized vapor barrier on each side and, with two crossed layers, I will have 4 vapor barriers. So-so. Not to mention that the cuts may be cotton, especially between the rafters ...
Otherwise, no problem for the CMV, the stage is already connected with a humidity sensitive system.

In summer, you have to manage well: Velux with external motorized roller shutters, which must be closed; open at night ...

Yes, whatever the insulation, it is not forbidden to use a little common sense.

Now, my passion that occupies me here is more gardening: the "Potager du Laesseux"

I happen to be passionate about it too since I own my house and I also watch your thread from time to time. Unfortunately, renovating my house still takes me too long to hope for a vegetable patch. Above all, my configuration is not ideal, because I am surrounded by oaks. It is a problem for the sun but also for the soil, because their roots are everywhere. And I have yet to find any fruitful experience of vegetable gardens near oaks. So I catch up on my pleasure garden where I experiment plants for Mediterranean gardens (in partial shade, it goes without saying ) and soil degradation with BRF. And I have flowers that I eat with my eyes, if I can't just eat them! But I'm dispersing.

Thank you

[Did67]

For VMC, in this kind of "casings", it is important to put the "nozzle" in the coldest place (in general the "corner" giving on the pinion). Or even put two, one at each corner!

For technical reasons, this is not the case with me, and I have a few small condensations there. There are few "movements of air", and in my case, about a third of the volume, with the bed, is without opening, on the gable side ... The staircase opens out roughly in the middle. And to the left of the stairs, on the other side therefore, there is the sanitary part (bed, WC), with the connection. I don't go as far as the second gable, I still have a "technical box", with passage of the chimney flues, pipes, ducts ... So it's more humid, but better insulated!

Condensation always takes place in the coldest place.

For your polyurethane sandwich, in my opinion, if your first barrier is well sealed, there is no risk of condensation ... Stick with the special insulating "scotches" that we use for thin insulation. I think you need to be inspired by what is done with thin insulation, your sheets will have a similar behavior: waterproof, reflective, risk of condensation ... You will have air circulation between your roof and your insulation ?

[chatelot16]

when you can put the thickness you want simple glass wool is the cheapest solution ... when the available thickness is limited it is the polyurethane foam which is the most efficient, it is waterproof therefore does not need a vapor barrier ... it is not

first message written with a new windows10 computer ... message not finished sent without express and impossible to erase it

[chatelot16]

when you can put the thickness you want simple glass wool is the cheapest solution ... when the available thickness is limited it is the polyurethane foam which is the most efficient, it is waterproof therefore does not need a vapor barrier ... it is not completely opaque to infrared so a metallic layer like survival blanket is useful ... multilayer insulation is useless because their multiple layer is useless, one would be enough, but oddly the simple metallic pet films are not available in the building while they are abundantly used for thermal insulation of airplanes ... and for airplanes the studies are serious so if it is used for airplanes it must be useful !

[Did67]

There are different thicknesses, so more or less "multilayers". I think this plays on the little "foam" that there is between each plastic film, to limit condensation.

Note that while insulating, it works the better the higher the radiation (clear weather).

I bought an anorak 30 years ago for a trip to Peru / Bolivia in summer (winter there). When you are active, it is spectacularly effective! I still have it !