Loft insulation - to top up or not? And other insulation musings

grumbler

ChasingtheWelshdream said:

The most pressing question is whether it is worth topping up the (old) 270mm existing loft insulation with another 100mm before we board it out (this weekend’s job)

Unless I misunderstand something, if you add insulation on top of the joists, boarding  becomes far more complicatd than a simple 'weekend's job'.

ChasingtheWelshdream

Loft legs and only partial boarding….

FreeBear

ChasingtheWelshdream said:

Loft legs and only partial boarding….

If you go for the XL legs (300mm long), you get extra space should you ever want to put more insulation down.

goldfinches

For the bay window it is definitely worth adding insulation underneath the window, it is also really worth putting up the sort of curtain rod that covers the whole bay and overlaps the wall at either side and then buying insulated curtains that hang the full height of the wall. If you can't insulate an external wall one possible alternative is to put bookshelves against it as that really does help keep a room warmer.

Bendy_House

What's the current recommendation for LI thickness? 300mm? 350mm?

If, at 270mm, your existing layer is 'almost' there, and to add taller floor legs a pain, my 'guess' is that - once you floor over 270mm - it'll be AS effective as 350mm. My reasoning would be that the top - ooh - 50 to 100mm of normally-laid LI will, in practice, have a lot of cold air percolating through it, so is unlikely to be anywhere as effective as the deeper layers. But, once you 'snugly' over-board - the new floor gently compresses the very top to close off the air gap there -  you will be greatly reducing this draught, and I 'suspect' making the whole depth significantly more effective.

Pure conjecture...

Ah, Build Regs - they are going to insist on the full depth anyway, aren't they?!

Bendy_House

The coombed ceilings - yes, line with Celo/Kings, and vapour-controlled p'board.

If headroom is an issue, then remove the existing first - messy, but surely worth it. This will allow you move part of the new thickness in between the rafters. Just ensure a min 50mm gap between the insulation and the roof covering, and don't block off either the top or where it joins the eaves.

You will surely get 2" in there, nicely flush with the lower edge of the rafters, any gaps 'foamed', and then fully overboard with whatever thickness you can get away with, even if only a further one inch. This will be truly transformative, even tho' still not to current regs (but will be getting close - your call whether going the final mile is worth the extra inch or so...)

Again, tho', will BC be INSISTING you do this to current standards?

ChasingtheWelshdream

In terms of getting BC control sign-off, our inspector is happy as long as we have 270 in the ‘flat’ loft areas and isn’t expecting the coombed parts to be upgraded so we can satisfy him easily. It was whether it is worth adding extra depth, which we have decided is better spent elsewhere.

The rest is us trying to make the rooms more comfortable where we can. Ceiling height or floor space isn’t an issue in most cases so we can overboard the coombed parts easily without it impacting the useable area.

A question regarding partially insulating a wall…

I am adding a radiator to an alcove. The only external wall area is under the window (where the radiator is going), 6-ish inches either side of the window and a few inches above the window.

The alcove is next to an unused chimney breast which houses our cooker. The rest  of the wall has kitchen cupboards.

Is it worth adding an inch insulation to this small area I can reach, or is that not worth worth it? I know I would need to think about the fixings etc, its whether that small area would give any returns in terms of comfort/heat retention.

Bendy_House

ChasingtheWelshdream said:

In terms of getting BC control sign-off, our inspector is happy as long as we have 270 in the ‘flat’ loft areas and isn’t expecting the coombed parts to be upgraded so we can satisfy him easily. It was whether it is worth adding extra depth, which we have decided is better spent elsewhere.

The rest is us trying to make the rooms more comfortable where we can. Ceiling height or floor space isn’t an issue in most cases so we can overboard the coombed parts easily without it impacting the useable area.

A question regarding partially insulating a wall…

I am adding a radiator to an alcove. The only external wall area is under the window (where the radiator is going), 6-ish inches either side of the window and a few inches above the window.

The alcove is next to an unused chimney breast which houses our cooker. The rest  of the wall has kitchen cupboards.

Is it worth adding an inch insulation to this small area I can reach, or is that not worth worth it? I know I would need to think about the fixings etc, its whether that small area would give any returns in terms of comfort/heat retention.

In that case, I would personally just overboard - snugly - the existing 270mm. I am pretty sure that, in itself, will improve it.

Coombed ceilings - do these, no question. Whether you strip off the existing first is your call. I would be tempted to do so, but it's a lot more work.

Hard to judge on the other 'partial' wall issue. I would say 'yes', even if it's to reduce the number of cold areas as much as possible, ones that could become magnets for condensation and mould. What I would also try and do is to move the rad to an internal wall, and consider a designer style if that helps. This would allow you to insulate as much of the ext walls as possible, without having to worry about mounting stuff on it afterwards. It would also hopefully make the rads an actual feature rather than a necessity - that might give your kitchen a 'lift'.

Also, whenever you can, try and oversize the rads so you can run them on cooler water.

FreeBear

ChasingtheWelshdream said: I am adding a radiator to an alcove. The only external wall area is under the window (where the radiator is going), 6-ish inches either side of the window and a few inches above the window.

The alcove is next to an unused chimney breast which houses our cooker. The rest  of the wall has kitchen cupboards.

If you are heating a kitchen, I can highly recommend plinth heaters - These fit in to the kickstrip along the base of your kitchen units, thus freeing up valuable wall space. You can get wet versions that plumb in to your existing central heating systems as well as electric versions (expensive to run), and combined wet/electric.

Got a wet plinth heater in my kitchen, and love the fact it blows warm air out at floor level to heat up toes (and the rest of the space). In a well insulated draught free house, there is no real need to mount a radiator under the window.

ChasingtheWelshdream

Thanks, interesting info for future. I will carry on with the radiator though as I have the rad already and we don’t have kickboards on our units. 

It can’t go anywhere else as there are no other spare walls, and is a chunky vintage style, so will work well visually. Whether I insulate that little bit of wall though…..