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Loft Insulation top up

Does what it says on the tin
richlist
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Re: Loft Insulation top up

#261709

Postby richlist » November 2nd, 2019, 4:54 pm

I'm not an electrician or builder with any expertise other than I've already done my own loft.
* I'd suggest that the electric shower cable, which is going to be 6mm or 10mm should be positioned above the insulation.
* Ideally any 13 amp cable is also above the insulation.
* Any downlighters should have fire hoods fitted in the loft.

AsleepInYorkshire
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Re: Loft Insulation top up

#261714

Postby AsleepInYorkshire » November 2nd, 2019, 5:16 pm

Snorvey wrote:I'm up the loft at the moment organising things so I can top up my loft insulation and then a partial flooring exercise using those plastic stilts.

Currently, there is 100mm of insulation (I know there should be at least 270mm, but the task of clearing decades worth of shite meant tit was 'out of sight, out of mind'.

Anyway, I'm finally getting on with it. A question re: cabling.

I've identified the shower cable. It's clipped along the top of the joists. I know I should not put insulation over this. The other cabling in the loft is all for lighting and is a mixture of normal pandants and recessed LED's in the bathroom. The older pendant cabling is passed through holes drilled in the joists. Am I ok to lay insulation over the top of this or should I try and keep it on top of the insulation?

There is also a cold water lagged pipe going across the loft to the shower. I guess I am definitely ok to insulate over the top of that?

Presumably you're aware but prudency demands I suggest you make sure you have adequate ventilation above the new insulation. This can come through the tiles if it's an old roof with no felt. Failing which you will need to consider ventilation trays along the eaves to keep a minimum 50mm gap between the roof felt and the insulation. May also need some cross ventilation through high level airbricks in the gable (if the structure has them). Try to avoid ventilation through the roof tiles if possible. Expense and creates a weak spot going forward where water could ingress and cause damage.

I took a "little Henry" into Mum's loft years ago. Two days later and black with soot we counted over 80 sacks of soot and plaster into the skip - very messy job. If I lived near you I'd swing round to help - as long as there was plenty of tea to drink :) Probably a good job I don't :)

Have fun :)

AiY

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Re: Loft Insulation top up

#261744

Postby AF62 » November 2nd, 2019, 9:17 pm

AsleepInYorkshire wrote:Presumably you're aware but prudency demands I suggest you make sure you have adequate ventilation above the new insulation. This can come through the tiles if it's an old roof with no felt. Failing which you will need to consider ventilation trays along the eaves to keep a minimum 50mm gap between the roof felt and the insulation. May also need some cross ventilation through high level airbricks in the gable (if the structure has them). Try to avoid ventilation through the roof tiles if possible. Expense and creates a weak spot going forward where water could ingress and cause damage.


After installing additional loft insulation a few years ago I noticed that condensation was occurring, and this was with plenty of space at the eaves to allow ventilation through there.

I was recommended these http://www.roofingsuperstore.co.uk/prod ... -vent.html and over the last couple of winters they have worked really well and eliminated (or massively reduced) the problem.

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Re: Loft Insulation top up

#261746

Postby AsleepInYorkshire » November 2nd, 2019, 9:36 pm

AF62 wrote:
AsleepInYorkshire wrote:Presumably you're aware but prudency demands I suggest you make sure you have adequate ventilation above the new insulation. This can come through the tiles if it's an old roof with no felt. Failing which you will need to consider ventilation trays along the eaves to keep a minimum 50mm gap between the roof felt and the insulation. May also need some cross ventilation through high level airbricks in the gable (if the structure has them). Try to avoid ventilation through the roof tiles if possible. Expense and creates a weak spot going forward where water could ingress and cause damage.


After installing additional loft insulation a few years ago I noticed that condensation was occurring, and this was with plenty of space at the eaves to allow ventilation through there.

I was recommended these http://www.roofingsuperstore.co.uk/prod ... -vent.html and over the last couple of winters they have worked really well and eliminated (or massively reduced) the problem.

Nifty product. Seems to have created some "cross" ventilation. Did you use many?

AiY

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Re: Loft Insulation top up

#261755

Postby paulnumbers » November 2nd, 2019, 10:45 pm

Snorvey wrote:I've just found my Atari ST computer and it's 80mb (serial port?) external hard drive and a pile of games.

Shall I boot it up and have a game or 12 of Gorf?

Tempting....


Bloody hell, external hard drive on the Atari ST, someone was rich!

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Re: Loft Insulation top up

#261758

Postby paulnumbers » November 2nd, 2019, 11:01 pm

Snorvey wrote:
paulnumbers wrote:
Snorvey wrote:I've just found my Atari ST computer and it's 80mb (serial port?) external hard drive and a pile of games.

Shall I boot it up and have a game or 12 of Gorf?

Tempting....


Bloody hell, external hard drive on the Atari ST, someone was rich!


Cost me an arm and leg that did. And sitting next to me right now is a 32gb pen drive that cost but a few quid.

Oh I wish they'd told us it would be like this.


My budget only stretched to the external floppy drive! I suspect it's still in my parents loft.

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Re: Loft Insulation top up

#261771

Postby richlist » November 3rd, 2019, 7:44 am

Why not wait until Labour win the General Election then you can get your loft insulated at taxpayers expense !

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Re: Loft Insulation top up

#261832

Postby AF62 » November 3rd, 2019, 1:35 pm

AsleepInYorkshire wrote:
AF62 wrote:
AsleepInYorkshire wrote:Presumably you're aware but prudency demands I suggest you make sure you have adequate ventilation above the new insulation. This can come through the tiles if it's an old roof with no felt. Failing which you will need to consider ventilation trays along the eaves to keep a minimum 50mm gap between the roof felt and the insulation. May also need some cross ventilation through high level airbricks in the gable (if the structure has them). Try to avoid ventilation through the roof tiles if possible. Expense and creates a weak spot going forward where water could ingress and cause damage.


After installing additional loft insulation a few years ago I noticed that condensation was occurring, and this was with plenty of space at the eaves to allow ventilation through there.

I was recommended these http://www.roofingsuperstore.co.uk/prod ... -vent.html and over the last couple of winters they have worked really well and eliminated (or massively reduced) the problem.

Nifty product. Seems to have created some "cross" ventilation. Did you use many?


I used ten, five each side of the roof, placed in alternate 'bays' between the trusses.

They were very easy to install, with the biggest difficulty navigating through the junk in the loft, as they just push down between the felt with a clip to stop them going too far.

The loft doesn't appear to be any colder or draughtier after them being installed, but the cross ventilation has been enough to stop the condensation and damp that was previously occurring.

For £24 for the ten from Amazon and half an hour's work, it was a quick and easy fix.

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Re: Loft Insulation top up

#262125

Postby fisher » November 4th, 2019, 9:09 pm

Snorvey wrote:I've identified the shower cable. It's clipped along the top of the joists. I know I should not put insulation over this. The other cabling in the loft is all for lighting and is a mixture of normal pandants and recessed LED's in the bathroom. The older pendant cabling is passed through holes drilled in the joists. Am I ok to lay insulation over the top of this or should I try and keep it on top of the insulation?


Putting insulation over electrical cables de-rates the cables - i.e. it means they can carry less current than if they were not under insulation. This usually means that you wouldn't put insulation over them if you can help it. For lighting cables in a loft they usually have much more capacity than they need particularly if all the lamps attached are low energy LED or CFC lamps rather than the old tungsten ones. I think you can probably put your insulation over your lighting cables if you have no choice without it causing a problem. There are some tables that you can find if you search which will outline the effect of various amounts of insulation on various categories of cable. Your lighting cable is probably 1.5mm2 cable which is rated up to a total of 20 amps if not run through insulation. Have a search on the effect of insulation on this and work out whether you would still have sufficient capacity. Check if it is 1.5mm2 cable that you have.

Don't put any insulation over the shower cable. It carries much higher current.

I am not an electrician so it would be worth seeing if someone can guide you who has electrical qualifications.

Here is an old discussion along similar lines: https://forums.moneysavingexpert.com/sh ... p?t=606627
Lots of others are available via a goole search.

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Re: Loft Insulation top up

#323617

Postby dspp » July 3rd, 2020, 9:04 pm

Snorvey wrote:....I'm not asking for anyone to say, 'yeah, go for it' btw.....but for someone to point out any glaring mistakes. Ta.


IMHO the 1.5mm2 that used to supply incandescent lights but now supplies LEDs will be absolutely fine if you just pile as much insulation as you like on it. As has been pointed out "cables laid in air" should be derated if insulated, but you have achieved a c. 90% derating by making the switch from incandescent to LED so you are good to go.

(I'm not part P qualified, so just my opinion of course.)

BTW the drilling through joists to run cables is good practice, not something to be frowned upon. I won't go into the details but it is quite correct.

regards, dspp


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