Green Building Forum - how to insulate bay window and porch

how to insulate bay window and porch

mattp — Tue, 18 Mar 2025 10:38:00 +0000

Thanks for all the comments and suggestions. I have read about using EPS beads in this way in Tony Cowling's draught-proofing book. It is very interesting that this works, and it would give unbeatable levels of insulation, but I would be worried to do this for the reasons that GreenPaddy outlined.

Periscope vents - I think I might just direct the air straight down behind the sleeper wall and not over the top of the wall plate unless I am missing something? There are loads of gaps in all the walls so air flow won't be an issue and I would have less floor area with only 50 mm insulation. I have an approx. 80 mm gap between the external wall and the first sleeper wall.

Insulation - I think you might be assuming the wood fibre I have got is in the form of rigid boards. They are squashy and fibrous (they maintain their shape, but you can pull them apart with your hands). They are these ones: https://www.buyinsulationonline.co.uk/product/steico-flex-036-wood-fibre-insulation-batts-575mm-x-100mm. The guy who delivered them asked me if I was feeding a horse . I was thinking of stuffing wood fibre or glass fibre down the sides of the room between the sleeper walls, although it might be too much of a faff getting a membrane in that space. I like the idea of putting kingspan over the wall plates on the sleeper walls since this has a higher insulation rating.

Pipe lagging for the MDPE pipe - I should have come on here a few months ago because I already bought some of the black nitrile foam stuff with only a 19 mm wall: https://www.pipelagging.com/armaflex-pipe-insulation-lagging-black-nitrile-foam-class-o-2m-28mm-19mm-wall. I calculated the 19 mm thickness based on this online calculator from Water Regs UK https://www.waterregsuk.co.uk/information/tools/pipe_insulation_tool/. If I assume -5C ambient temperature and +1C supply temperature I get the recommended 12 hours protection. Maybe I should have gone for more safety margin, although I am in Southampton which does not get quite as cold as some parts of the UK in winter.

Rodents - I hadn't really considered this! I bet rats and mice would like chewing nitrile foam. Thinking about it, they would probably also like to destroy wood fibre insulation. Maybe my best option is to make sure there is no way they can get in and hope for the best?

By the way, how do I add links here?

how to insulate bay window and porch

djh — Wed, 19 Mar 2025 09:48:28 +0000

Posted By: mattpBy the way, how do I add links here?

Links and quotes are somewhat contradictory. To get nicely formatted blue quotes you have to select the 'Html' radio button at the bottom of the text box (on some browsers!). To get an active link you have to select the 'Text' button :(

how to insulate bay window and porch

djh — Wed, 19 Mar 2025 09:56:30 +0000

Posted By: mattpPeriscope vents - I think I might just direct the air straight down behind the sleeper wall and not over the top of the wall plate unless I am missing something? There are loads of gaps in all the walls so air flow won't be an issue

That sound slike a good idea.

I was thinking of stuffing wood fibre or glass fibre down the sides of the room between the sleeper walls

Glass fibre is really itchy. Use rock wool in preference.

Pipe lagging for the MDPE pipe

What does the pipe carry? How often does water run through the pipe?

Rodents - I hadn't really considered this! ... Maybe my best option is to make sure there is no way they can get in and hope for the best?

Yes, keeping them out is definitely best. Mice can get through very small gaps.

how to insulate bay window and porch

mattp — Wed, 19 Mar 2025 12:31:33 +0000

Posted By: djhWhat does the pipe carry? How often does water run through the pipe?

It's the main water supply to the house. It runs from the meter under the pavement to the stop tap in a room at the back of the house (where the boiler is). When I moved in there was a lead pipe coming up through the floorboards behind the front door, so I wanted this changed. It would have been nice to have it buried down the side of the house and come up in the boiler room, but that would have involved digging up a lot of concrete and crossing a power line and drains. So I had it run under the floor - it's why all the floorboards were taken up originally. It's a 25 mm MDPE pipe.

The main risk I can think of is that there is a cold snap and we are away so no one is using water.

how to insulate bay window and porch

djh — Wed, 19 Mar 2025 15:43:11 +0000

Posted By: mattpThe main risk I can think of is that there is a cold snap and we are away so no one is using water.

It might be worth putting a cheap thermometer down there temporarily (if you've got some way of logging it) to see how cold it actually gets. It can't see the sky from under the floor so there's no radiative loss and I doubt it gets very cold in the house even when you're away. You could leave a low-powered heater on in that room when you're away or fit a trace heater to the pipe itself if you were very paranoid. But I doubt there'll be a problem in reality.

how to insulate bay window and porch

Peter_in_Hungary — Wed, 19 Mar 2025 19:32:49 +0000

Posted By: mattpThe main risk I can think of is that there is a cold snap and we are away so no one is using water.

It is my understanding and my practical experience having MDPE pipe around my farm is that the pipe will take repeated freeze / thaw cycles with out damage. Note - the same can not be said about the fittings.

The biggest problem I have had with a frozen MDPE pipe is thawing it out - a gas torch is not a good idea !!

how to insulate bay window and porch

GreenPaddy — Wed, 26 Mar 2025 08:01:21 +0000

late to the party, but re. mains water pipe, whilst the water supplier are responsible up to your boundary (or the valve close to it), and you are responsible for the service pipework from that point, that doesn't mean you can choose to do with it what you think is OK. There are water byelaws, and your water authority has requirements for how you deal with the pipework (eg. minimum 750mm below ground level, rising in a duct with insulation as it comes into the house, insulation of exposed pipework. You can't decide you don't think it will freeze often, so not bother.
Hence my suggestion about vermin resistant insulation on the exposed pipe below floor (ie, outside the thermal envelope). I ain't the pipe police, but you should make yourself aware of your responsibilities, before carrying out works. That's a pain, cause there are lots of codes, regulations, etc, sometimes things that contractors don't even know about.
Just sayin'

how to insulate bay window and porch

mattp — Wed, 26 Mar 2025 10:05:09 +0000

Posted By: Peter_in_Hungary
It is my understanding and my practical experience having MDPE pipe around my farm is that the pipe will take repeated freeze / thaw cycles with out damage. Note - the same can not be said about the fittings.

The biggest problem I have had with a frozen MDPE pipe is thawing it out - a gas torch is not a good idea !!

Thanks, that is reassuring. There will be no inaccessible fittings - only the pipe.

Posted By: GreenPaddylate to the party, but re. mains water pipe, whilst the water supplier are responsible up to your boundary (or the valve close to it), and you are responsible for the service pipework from that point, that doesn't mean you can choose to do with it what you think is OK. There are water byelaws, and your water authority has requirements for how you deal with the pipework (eg. minimum 750mm below ground level, rising in a duct with insulation as it comes into the house, insulation of exposed pipework. You can't decide you don't think it will freeze often, so not bother.
Hence my suggestion about vermin resistant insulation on the exposed pipe below floor (ie, outside the thermal envelope). I ain't the pipe police, but you should make yourself aware of your responsibilities, before carrying out works. That's a pain, cause there are lots of codes, regulations, etc, sometimes things that contractors don't even know about.
Just sayin'

Thanks. I am trying to do this by the book, but you are right that it's not easy to find all the information. I got a plumber to do this installation for me. He dug a trench from the front of the house to the boundary and ducted the pipe up into the house. He didn't bother to insulate any of it though. Before it was connected, I had a visit by someone from Southern Water and the inspector said the installation met the requirements, but that there was no insulation and that this was required. It was however his last day before leaving Southern Water to start another job and he said that to avoid more weeks of delay if I gave him my word that I would insulate the pipework then he would sign it off. So a couple of weeks later some contractors appeared and dug up the pavement to connect the new pipe.

Unfortunately I didn't think to ask the inspector what insulation I should use so I have been googling ever since! The website I linked to (Water Regs UK) seems to be an official source of guidance and I used their calculator to arrive at 19 mm insulation being suitable. However I can't find any specific information from Southern Water about local requirements re. type/thickness of insulation, or worst case environmental conditions to be able to withstand, so I used my own worst case scenario of -5C under the floor and (Water Regs UK recommendation) 12 hours protection.

I suppose I could just phone Southern Water and ask for their guidance, but I am slightly hesitant to do that, since as far as they know the installation is already insulated.

I know that I do have a slight problem with the ducting into the house, knowing what I know now. It has been done with a 55 mm pipe, whereas a wider diameter should have been used to accommodate more insulation. Here I think I will just squirt expanding foam down the sides as best as I can and then insulate properly from where the ducting pokes out of the concrete in the underfloor void.