The significance of the air gap

[Nygge72]

Hi, does the size of the air gap between the insulation and panel affect the insulation capability? I'm considering about 25mm or 45mm in this case.

I'm in the process of glazing an existing terrace and struggling with how to place the panel without extending too far out. I have to reframe a bit which means I need to use a 45x45 on top of the existing studs. I'm thinking if I can place the wind barrier between the existing stud and my new 45x45, and then put the panel directly on the 45x45, instead of having to place the air gap on the outside of the 45x45.

But I'm concerned if the gap between the panel and insulation becomes too large. The insulation is mainly to retain some heat, not to keep it warm during winter. So perhaps I'm worrying unnecessarily =) But I thought I'd throw the question out to the wise in this group.

 

[Silver78]

What type of insulation should you use?

 

[Nygge72]

What type of insulation will you use?

In this case, it will be mineral wool as it's the wall I will be placing it on. Insulation that is leftover from adding extra insulation to an outer wall.

 

[Nygge72]

Changing my question a bit. Do you even need an air gap with Cellplast EPS? Then maybe it's better if I use that instead as insulation.

 

[Silver78]

The minimum requirement is 25 mm. But it is important that it is sealed in the transition roof/wall. The risk with too large a gap is that you can get too much cold wind inside and thereby get the condensation point closer to the construction. But since it involves so little insulation, I would say that a lot of heat will escape, drying out so an air gap of 25 mm is more than sufficient. The question then is how much heat is available here. Sealing against diffusion can lead to the condensation point being on the wrong side if the space is sparsely heated. But again, it is usually a non-issue when insulating thinly. Keep in mind that you avoid a whole cooling down by insulating the floor.

 

[Silver78]

Single-stage sealing is not recommended. Many have had problems with it. However, cellplast is quite sensible as it does not retain moisture in the same way. However, cellplast does not transport moisture, so you still need to seal against diffusion and have an air gap outside.

 

[Nygge72]

My idea is to set it up in the following way:

1. Panel
2. 45x45
3. Windproof fabric
4. Insulation
5. Some kind of inner panel.

This panel wall will be under a glass section, so it will not go up to the ceiling. Since the conservatory is small and will be glazed, it will likely generate a lot of heat as it faces south. Thus, a lot of warm air will be pushed out, and my intention is not to have a too dense construction overall. For example, the roof is not insulated. The idea is more that the glazing should protect against the wind, during autumn/spring.

 

[Nygge72]

With a bit of consideration, it will probably be like this: next to the glass section (on the sides), I'll place my 45x45 timber, while under the glass section where I will set the panel, I'll place 2 pieces of 25mm battens, so I can fit the wind barrier in between and have an air gap of 25 mm without extending more than my 45x45 by a few mm.

 

[Silver78]

You might need to rethink a bit about insulation. If you don't have good insulation in the ceiling and floor, you won't get much effect from insulating the outer wall. If you're after wind-protected properties, you'll get equally good properties with a thin layer of cellosa between the outer and inner wall. Then you'll get a diffusion-open construction that isn't sensitive.

 

[Nygge72]

You might need to reconsider your approach regarding insulation. If you don't have good insulation in the roof and floor, you won't get much effect from insulating the outer wall. If it's the wind-protected properties you're after, you'll get similar benefits with a thin layer of cellulose between the outer and inner wall. This way, you'll have a diffusion-open construction that is not susceptible.

the insulation in the wall is primarily to withstand a bit of heat in the morning

 

[Rabbithole]

28 or 45mm air gap should not make a difference. But you should have a wind barrier on the insulation.