Air source heat pumps

[WouldBe]

an insulating layer on a wall means the outside-facing side of the insulation is colder that it would be, which means water is more likely to condense (I think) which gives possibility for mould.

The insulation shouldn't be any colder than the outside wall itself so shouldn't be anymore likely to cause mould.

 

[Chz]

Should be over 60 to kill any bacteria.

Yes, 48 is a normal setting for a combi boiler but you need to heat a standing water tank to 60 at least once a week.

 

[teuchter]

an insulating layer on a wall means the outside-facing side of the insulation is colder that it would be, which means water is more likely to condense (I think) which gives possibility for mould. I'm not sure why that doesn't happen with insulation on breathable walls.

Do you mean, if the insulation is breathable, then doesn't that mean that it will be allowing humidity to pass through and condense behind the insulation?

In the case of the very thin insulation you have, I think part of the answer is that the insulation effect is fairly minor so under most conditions the wall is still actually kept a bit warm and the dew point stays within the thickness of the wall.

The thinking behind "breathable" internal wall insulation often tends to be part of a strategy to let moisture in the wall dry out towards the inside, and sometimes that's because there's a worry that the wall gets damp from external sources and then won't dry out in the same way that it used to (prior to being insulated).

This can all get a bit complicated because the best strategy will depend on the whole wall buildup, the climate, and various other stuff, and often there's a variation in opinion depending who you ask.

Worst case scenario can be totally non breathable insulation, thick enough to bring the dew point to the surface of the wall behind it, and then some way for humid internal air to get to that surface, which is one reason to be cautious about using battens for internal insulation because it creates an air cavity which can distribute that humid air unless it's fully sealed off from the internal space. That's why the advice now normally is to try and stick direct to the wall with no air gap behind.

 

[WouldBe]

which is one reason to be cautious about using battens for internal insulation because it creates an air cavity which can distribute that humid air unless it's fully sealed off from the internal space. That's why the advice now normally is to try and stick direct to the wall with no air gap behind.

If you've got uneven walls you'll always end up with gaps behind the insulation unless you spray foam the walls.

Better to do the job properly and seal it or there's not much point doing it as you'll still be losing heat.

 

[teuchter]

The insulation shouldn't be any colder than the outside wall itself so shouldn't be anymore likely to cause mould.

If the back of the insulation isn't colder than the inner face of the wall previously was, then the insulation isn't working.

 

[lazythursday]

Should be over 60 to kill any bacteria.

Which it does once a week.

 

[WouldBe]

If the back of the insulation isn't colder than the inner face of the wall previously was, then the insulation isn't working.

Obviously but I was on about the original external wall not the new interior wall.

 

[teuchter]

Obviously but I was on about the original external wall not the new interior wall.

Not sure what you mean. We're taking about an external wall which has had insulation applied to its internal face.

 

[two sheds]

Do you mean, if the insulation is breathable, then doesn't that mean that it will be allowing humidity to pass through and condense behind the insulation?

In the case of the very thin insulation you have, I think part of the answer is that the insulation effect is fairly minor so under most conditions the wall is still actually kept a bit warm and the dew point stays within the thickness of the wall.

Yes I think that covers it. The insulation is thin but has made a noticeable difference because the room seems to warm up more quickly.

The thinking behind "breathable" internal wall insulation often tends to be part of a strategy to let moisture in the wall dry out towards the inside, and sometimes that's because there's a worry that the wall gets damp from external sources and then won't dry out in the same way that it used to (prior to being insulated).

Interesting - I did read that with rab (stone/clay/stone) walls during winter the moisture gets absorbed from the rooms into the wall and dried out in summer.

This can all get a bit complicated because the best strategy will depend on the whole wall buildup, the climate, and various other stuff, and often there's a variation in opinion depending who you ask.

Worst case scenario can be totally non breathable insulation, thick enough to bring the dew point to the surface of the wall behind it, and then some way for humid internal air to get to that surface, which is one reason to be cautious about using battens for internal insulation because it creates an air cavity which can distribute that humid air unless it's fully sealed off from the internal space. That's why the advice now normally is to try and stick direct to the wall with no air gap behind.

One thing I've done that I'm really not sure about is in my bedroom upstairs. The roof slopes down at about 30 degrees and there's a 3-ft high cupboard stretching across with a couple of shelves at the front, and the space behind dropping to floor level (hope that's clear).

The roof is plasterboard so a bit insulated but the space at the back of the cupboard has a gap and gets cold (I was getting some mould on things on the cupboard shelves). I've tried to insulate it myself with some 1-foot high ply across the back of the shelves with as much sheeps wool insulation behind it as I can stuff in there.

However. There are gaps at the top of the ply and I think I should get somebody proficient to do the whole thing properly. I've been occasionally aiming a dehumidifier in there but am concerned in case it's getting mouldy back there.

 

[newme]

Perhaps worth investigating again at some point now things have moved on a bit? And the renewable heating incentive is gone but you can get the new boiler upgrade grant.

I can't get anything, council house. I got put on "a list" as objecting to having one, told the boiler guy from the council that and he said what list lol? Not a fan of them himself it seems and surprisingly senior. They had made out like if my boiler failed I'd just get air source stuck in, which suits us in no way at all. Like he said, ok you have no boiler, which is fastest way for them to fix the problem? New oil boiler with existing everything or replacing half the house with you already resistant to the idea and no space or time to do it? Plus £500 a year for heating is not exactly going to get any better regardless of the system employed unless its free solar and huge amounts of capital investment in other bits and pieces they don't have cash for.

Should be over 60 to kill any bacteria.

Well yeh bang on, which works fine currently and I can't see how its going to be any improvement to have it sat at lower than useful temps mostly while we also don't have a continuous heating requirement, no underfloor and no use in general for it. Had two rads on in the kitchen on low to dry bean bag out and had requests we could turn it off as it was too hot. Had closed my door but did notice the heat boost from downstairs when I opened the door. Just doesn't need much here for whatever reason.

 

[two sheds]

If you've got uneven walls you'll always end up with gaps behind the insulation unless you spray foam the walls.

I've thought about battens with sheepswool insulation for my place which is also uneven, and which I presume would also be good.