I am looking at the walls of different house manufacturers and one of them has a wall they claim is energy efficient, constructed approximately as follows:
(From outside to inside)
panel - windproof fabric/paper - 45 mm mineral wool - 195 mm mineral wool - plastic - 45 mm mineral wool - wood fiberboard - gypsum board
I might have forgotten something, and I'm not sure if the 195 mm part is one or several layers. It's a 45 mm installation layer inside the plastic.
Anyway, I'm wondering if it might be a good idea to have 70 mm instead of 45 mm for the installation layer.
I've seen that Paroc has a similar wall description where they have 45 - 170 - 70 from outside to inside if I remember correctly.
Could having 70 mm internally instead of 45 cause problems, aside from the fact that it might be more difficult to fit 70x45 studs instead of 45x45...
Maybe it would be better to have 70 mm inside the panel instead of 45 (so build insulation outward)?
(From outside to inside)
panel - windproof fabric/paper - 45 mm mineral wool - 195 mm mineral wool - plastic - 45 mm mineral wool - wood fiberboard - gypsum board
I might have forgotten something, and I'm not sure if the 195 mm part is one or several layers. It's a 45 mm installation layer inside the plastic.
Anyway, I'm wondering if it might be a good idea to have 70 mm instead of 45 mm for the installation layer.
I've seen that Paroc has a similar wall description where they have 45 - 170 - 70 from outside to inside if I remember correctly.
Could having 70 mm internally instead of 45 cause problems, aside from the fact that it might be more difficult to fit 70x45 studs instead of 45x45...
Maybe it would be better to have 70 mm inside the panel instead of 45 (so build insulation outward)?
I think it seems like a perfect wall, because that's exactly how I build.Prosit said:
As far as I understand, 45 mm should suffice. The electrical wiring has plenty of space, and I think water pipes and such will also fit.
With walls that thick, it won't cause any problems except for what you mentioned. But with, for instance, 95mm or 120mm and then plastic and a 70mm inside the plastic, the dew point could end up inside the plastic, which is quite bad, to say the least.
I would go exactly as in the first suggestion in the post if no greater total thickness is desired.
But then I would start thinking along the lines of:
from inside outwards
45mm installation space.
145mm load-bearing stud framework. (Where the roof truss load, etc., is managed)
120-170 mm secondary stud framework, with offset studs compared to the primary framework. Only the facade is supported by this.
Exactly how to do something like this first sounds easy in theory, but I don't really know how much extra hassle there is in the end. For instance, all window openings probably need to be a bit more complicated.
I don't know how much freedom I have with this house manufacturer, but I have previously said that I want the inside open, so there should not be major problems with switching 45 mm for 70 mm inside.
I think it should work for them to switch 45 mm outer to 70 mm too without much hassle, but they are probably not too keen on replacing parts of the load-bearing framework - and it's probably questionable to have a secondary framework with, for example, cross bracing on the outside.
In any case, my idea with all this is to get additional insulation, I'm looking at various recommendations, and they advocate for 300 insulation in walls, but the 285 they have in their "energy-efficient wall" is not so far off, so maybe it's unnecessary to try to struggle for about 25 mm extra...
I think it should work for them to switch 45 mm outer to 70 mm too without much hassle, but they are probably not too keen on replacing parts of the load-bearing framework - and it's probably questionable to have a secondary framework with, for example, cross bracing on the outside.
In any case, my idea with all this is to get additional insulation, I'm looking at various recommendations, and they advocate for 300 insulation in walls, but the 285 they have in their "energy-efficient wall" is not so far off, so maybe it's unnecessary to try to struggle for about 25 mm extra...
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Hey.
In that case, put 45x70 on the inside, as it's probably the easiest to deal with the supplier. It works fine either way. But it's certainly trickier to get it in place, because with 45's you just nail them on with 100mmx3.4 nails, right through. With 45x70, it becomes expensive with nail angles or long screws, or complicated with skew nailing, etc.
A possible alternative might be horizontal 45's and then another layer of vertical 45's again. And the plastic either 45 or 90mm into the wall.
If it’s single gypsum board, the latter has an advantage. If it's OSB+gypsum on the walls, it probably doesn't matter from that viewpoint.
In that case, put 45x70 on the inside, as it's probably the easiest to deal with the supplier. It works fine either way. But it's certainly trickier to get it in place, because with 45's you just nail them on with 100mmx3.4 nails, right through. With 45x70, it becomes expensive with nail angles or long screws, or complicated with skew nailing, etc.
A possible alternative might be horizontal 45's and then another layer of vertical 45's again. And the plastic either 45 or 90mm into the wall.
If it’s single gypsum board, the latter has an advantage. If it's OSB+gypsum on the walls, it probably doesn't matter from that viewpoint.
Member
· Norrbotten
· 3 390 posts
45x70 sounds good inside. I'm currently building with (from the outside in) Panel, nail battens, wind barrier, horizontal 95, vertical load-bearing 195, plastic, horizontal 45. What I experience in the middle of the construction is that RIR for water runs fits best in my 70 mm space if you want to bend them for a 90-degree pass-through. It can also be solved with a junction box. In my case, these will primarily be located in the ceiling where the installation space is 95 mm, but I will probably still have to handle some outlets from the wall.
Hmm, that's an interesting thought. For my part, it's RIR that's needed too, they should come vertically from the floor.norrbottenstorpet said:
How do you handle the attachment of your outermost 95s?
IF I understand correctly, you have 45 on the inside and therefore encounter difficulties with the RIR routing?
Member
· Norrbotten
· 3 390 posts
Just a plumber's words, that 70 mm is needed if you work with bent pipes. I think something like this http://www.rinkabyror.se/?showart.aspx?id=918 solves it all within a shorter installation dimension. Personally, I'm not quite there yet...
According to information, the bending angle requires 70 mm see http://www.rinkabyror.se/?showart.aspx?id=2857
According to information, the bending angle requires 70 mm see http://www.rinkabyror.se/?showart.aspx?id=2857
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I'm renovating my house and in my installation layer, I'm using 45*45, mainly because I don't want to extend inward and take up existing space.
I'm using PEX pipe systems in the installation layer plus electricity. I'm using Uponor's bending fixtures to bring the pipes out of the wall at 90 degrees. It works well as long as there isn't a stud right behind where the fixture needs to go (I put a little extra age-resistant tape right behind the fixture to reinforce the plastic a bit). But of course, 70 mm would have been a bit easier. It gets a little more difficult for me in the corners, since my pipes don't come from below.
Good luck
/PC
I'm using PEX pipe systems in the installation layer plus electricity. I'm using Uponor's bending fixtures to bring the pipes out of the wall at 90 degrees. It works well as long as there isn't a stud right behind where the fixture needs to go (I put a little extra age-resistant tape right behind the fixture to reinforce the plastic a bit). But of course, 70 mm would have been a bit easier. It gets a little more difficult for me in the corners, since my pipes don't come from below.
Good luck
/PC
Member
· Norrbotten
· 3 390 posts
Sturdy screws and some solid 90-degree angle irons (yes, I know they create a bit of a thermal bridge, but you don't need many to make it stable)Prosit said:
The plastic should be a maximum of 1/3 into the insulation is what I've heard somewhere.
Actually, it's not that hard to figure out.
+20 inside and -30 outside gives a 50-degree temperature difference, meaning the zero point is at 20/50 or 40% into the insulation. If you then place the plastic at a maximum of 33% in, the moisture in the wall won't freeze.
However, the dew point can end up almost anywhere depending on the humidity in the house, but as long as the moisture doesn't freeze, it will dry out again.
Now, I'm not an expert on this, so consider it a calculation example.
Actually, it's not that hard to figure out.
+20 inside and -30 outside gives a 50-degree temperature difference, meaning the zero point is at 20/50 or 40% into the insulation. If you then place the plastic at a maximum of 33% in, the moisture in the wall won't freeze.
However, the dew point can end up almost anywhere depending on the humidity in the house, but as long as the moisture doesn't freeze, it will dry out again.
Now, I'm not an expert on this, so consider it a calculation example.
Member
· Norrbotten
· 3 390 posts
If I remember correctly, the rule of thumb is a maximum of 1/3 of the total insulation thickness.
Of course, you can calculate it, using an energy calculation so that you get an estimated temperature at the plastic and compare this with dew point tables.
Of course, you can calculate it, using an energy calculation so that you get an estimated temperature at the plastic and compare this with dew point tables.
The rule of thumb, as mentioned, is 1/3.
I don't think this is particularly theoretically determined but probably an empirically determined rule of thumb.
You can calculate dew points quite easily. There are, (in addition to formulas), tables of relative humidity (rH) and corresponding absolute humidity (aH).
When indoor air, which has a certain rH, is cooled down the closer it gets to the outer side of the wall, the rH increases (the same aH becomes higher rH at lower temp).
And when rH reaches 100%, water simply precipitates in the insulation and damage to the wall begins.
http://sv.wikipedia.org/wiki/Luftfuktighet
A faster way is this ready-made table with rH reduction vs temperature increase.
final table ... http://www.lfs-web.se/fukt.htm
Two calculation examples:
200mm insulation in the wall, plastic 50mm in, i.e., 1/4 in.
20° in the room, 8° outside. -> 12° temperature difference -> 17° at the plastic
dT = 3° means that rH must be at least 17% below 100% to avoid condensation at the plastic.
This works as long as rH inside is a maximum of 83%.
20° in the room, -12° outside -> 32° temperature difference -> 12° at the plastic.
dT = 8° means that rH must be at least 37% below 100% to avoid condensation at the plastic.
This works as long as rH inside is a maximum of 63%.
Then it sorts itself out a bit. In a heated house, we automatically get drier air as soon as the outdoor temperature drops.
I also think the margin should be a bit larger than this. Because 99% rH inside the wall may not condense moisture, but microorganisms and mold thrive just as well.
I don't think this is particularly theoretically determined but probably an empirically determined rule of thumb.
You can calculate dew points quite easily. There are, (in addition to formulas), tables of relative humidity (rH) and corresponding absolute humidity (aH).
When indoor air, which has a certain rH, is cooled down the closer it gets to the outer side of the wall, the rH increases (the same aH becomes higher rH at lower temp).
And when rH reaches 100%, water simply precipitates in the insulation and damage to the wall begins.
http://sv.wikipedia.org/wiki/Luftfuktighet
A faster way is this ready-made table with rH reduction vs temperature increase.
final table ... http://www.lfs-web.se/fukt.htm
Two calculation examples:
200mm insulation in the wall, plastic 50mm in, i.e., 1/4 in.
20° in the room, 8° outside. -> 12° temperature difference -> 17° at the plastic
dT = 3° means that rH must be at least 17% below 100% to avoid condensation at the plastic.
This works as long as rH inside is a maximum of 83%.
20° in the room, -12° outside -> 32° temperature difference -> 12° at the plastic.
dT = 8° means that rH must be at least 37% below 100% to avoid condensation at the plastic.
This works as long as rH inside is a maximum of 63%.
Then it sorts itself out a bit. In a heated house, we automatically get drier air as soon as the outdoor temperature drops.
I also think the margin should be a bit larger than this. Because 99% rH inside the wall may not condense moisture, but microorganisms and mold thrive just as well.
OK, thank you very much! I'll probably do some more calculations on that.Mikael_L said:
I'm wondering if one improves their situation somewhat by using, for example, linen insulation (http://www.isolina.com/se/isolering.cfm) or wood fiber boards (http://www.novator.se/kretslopp/0204/s10.pdf) inside the plastic - it might not make a difference? It may still get just as humid in the walls, but perhaps an opportunity to dry out differently than with mineral wool?
Having linen or wood fiber might only be beneficial if you have it throughout and a diffusion-open fabric instead of plastic?
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