lagging rafters

Greenst

I live in a cold 1930s housei can't have cavity wall insulation the loft floor is lagged but about 15 years ago so not up to todays standards or thickness. It's also fully boarded and there's a lot of 'stuff' up there so a major job to clear it out, but also a major job to take up all the flooring. I would then have to have the joists raised to accomodate thicker lagging. Been looking at lagging the rafters instead. Kingspan celotex is working out mega expensive. But I am wondering if I can use normal floor lagging as its much cheaper as long as I leave a 50ml gap to the tiles ? Has anyone done this with success?

Greenst

Anyone out there??? Anyone done their loft with the kingspan rigid foam? How had it worked out? Any answers gratefully received!!! Really want to do this before it gets really cold!

misa.blue

We also want to insulate roof between the rafters and all the Space blankets are so expensive :eek: We want to use the loft as hobby room in the future, therefore don't want to insulate floor..

Chunks

If you search the forum, there's a lot of info available. This is just an example which covers among other things the fix to avoid having to 'have the joists raised' (post 9):

https://forums.moneysavingexpert.com/discussion/3560749

Greenst

Thanks for that but it talks about lagging the joists I am looking for info on lagging the rafters economically. Can the usual type of loft lagging be used to lag the rafters ? From what I have read on internet and my very old DIY book I need to leave a 50 ml gap between the insulation and type roof to stop condensation forming. Loft lagging will work out significantly cheaper than solid foam kingspan type products.

Ben84

Lagging the rafters means insulating a much greater surface area than the attic floor, so it costs more. It also raises issues with ventilation. Generally people only do this so they can make the attic part of the internal heated space of the house.

You may be able to evade some of the problems by doing the loft a section at a time. Move everything to one half, lift the boards, insulate and replace then move everything to the finished side so you can work on the unfinished side.

designermatt_2

Don't lag your rafters. You will need to leave a minimum of 50mm air gap between the felt and the insulation, and will need to make a Building Regs Application.

Use Sapce board which is a semi dense polystyrene board which can sit above your ceiling joists prior to laying down your boards again for storage. Likely you have 100mm Glass fibre between 100 mm joists, if you combine this with two layers of space board you will achieve the modern standard of 0.16 'U'-Value. (The lower the better)

robotrobo

Greenst wrote: »

I live in a cold 1930s housei can't have cavity wall insulation the loft floor is lagged but about 15 years ago so not up to todays standards or thickness. It's also fully boarded and there's a lot of 'stuff' up there so a major job to clear it out, but also a major job to take up all the flooring. I would then have to have the joists raised to accomodate thicker lagging. Been looking at lagging the rafters instead. Kingspan celotex is working out mega expensive. But I am wondering if I can use normal floor lagging as its much cheaper as long as I leave a 50ml gap to the tiles ? Has anyone done this with success?

hi greenie.
i have the same problem or similar to yours my loft space in my bungalow as had a floor put in by the previous owner & there is very limited space to work as you need to be on your knees. while i have very good access & lighting up there it is tight for working in at my age & mobility!!, there is a small amount of lagging under the floor approx 2" & like you i have stowed quite a bit of allsorts up there.
what i am thinking of doing is leaving the boarding down & put the insulation on top of the existing boarding !, surely this will slow the heat loss down ?.
also have a car boot sale to get rid of the unwanted items we do not need & then i can stow the remainder of the stuff down the centre of the loft walkway (crawlway) which will not have the new insulation on , at the moment i have even put the old clean carpet left in the loft.
we are retired & we like the bungalow warm in the daytime especially , but i am reasonably happy with my last yearly bills before the big rises, but always looking to reduce the energy costs in any way thats still comfortable to us.
i look at it like this , a pint of beer costs £3 !!! it doesnt cost much more than that to keep warm all day:beer:.
kind regards

27col

There is absolutely no point in lagging the rafters unless you are intending to use the roof space to live in, or for a hobby space. All you are doing is to ensure that you have nearly doubled the volume to be heated. You need to prevent heat loss from the rooms below the roof floor. This involves lagging the roof floor, not the roof rafters.

supermonkey

designermatt wrote: »

Don't lag your rafters. You will need to leave a minimum of 50mm air gap between the felt and the insulation, and will need to make a Building Regs Application.

Use Sapce board which is a semi dense polystyrene board which can sit above your ceiling joists prior to laying down your boards again for storage. Likely you have 100mm Glass fibre between 100 mm joists, if you combine this with two layers of space board you will achieve the modern standard of 0.16 'U'-Value. (The lower the better)

Agreed.... your roof is a "cold roof". You canot change it to a "warm roof" with consequences.

Poosmate

This is probably a really dumb idea but I was thinking of pinning or nailing quilts to the rafters to try to keep a little extra warmth in my loft. I have a cold water storage tank up there and am really worried that one day if it gets cold enough outside the pipes will freeze.

My house is always very cold and my main heat source is a gas fire in my lounge which doesn't seem to throw out much heat. A couple of winters ago the temperature in my bathroom was just 5 degrees so I was really worried about how cold my loft space was. I've bought a couple of oil filled radiators though which I use when it gets really cold.

I have a few old quilts and thought if I attach them to the rafters it might keep a little heat in + I free up the storage space they're taking up! Anyone think this would work? Even if it only made 1 degree of difference I think it would be worth it! And is it something the OP could do as a temporary fix?

Thanks

Poo