loft insulation in thatched cottage

[shobo]

Morning all,

I am lucky enough to own a stone-built listed thatch.
I have no central heating. I have electric heating which I am quite happy with, it is effective and not expensive (I have the option of using a fireplace too). However the bedrooms would benefit from loft insulation, I feel. They have traditional lath and plaster ceilings, in good condition. I have electric cabling on the loft floor, all of it specified against rodents and fire.

I am thinking of laying rolls of rockwool in the loft. Factors I have considered are:

- the floor of the loft is in good condition, with the topside of the lath and plaster showing between the beams.
- there is very little thatch waste on the floor.
- the thatch itself is in good condition, it won't need replacing for many years (hence the insulation I put in would not get disturbed by the thatch replacement process).
- there is a cold water tank and pipework in the loft, and I am aware that insulation would cause the loft to become colder in winter, however I am not concerned about the small risk of pipes freezing.
- there are no noticeable draughts in the roof space - though I imagine air will slowly convect through the thatch.

Before going ahead and laying the insulation, are there any factors I might not have thought of, anyone ? Any possible effects on the ceiling plaster, or the thatch ? giving refuge to rodents ? anything ... ?...

Thankyou.

 

[MikeG]

You should of course insulate over the water tank and pipes, and not under them, thus keeping them within the heated and insulated envelope of the building. Other than that, I wish more people would do this, and more power to your elbow.

 

[Flyfisher]

Might the existing electrical cables need reviewing if they are now going to be insulated rather than in free air?

 

[shobo]

Thankyou MikeG

 

[shobo]

Thankyou FlyFisher.
I don't know ! I'm hoping not. I recently had my electrics recertified, and the electrician was happy with the arrangements in the loft. Now, the PVC cables on the floor of my loft have metal covers on them, but they do not cover all of the wires, because they are very crude. It is a condition of insurance that cables in the loft are either re-routed out of the loft, or protected in this way. I am surprised that this protection is good enough, because it supposedly protects against rodents chewing the cables. The metal covers would not stop this, because the covers are incomplete. Mice would easily be able to find a place to chew. On the other hand, the metal covers could also protect against a simultaneous fault in the wiring and straw having fallen. But the electrician who came to recertify assured me that the reason for the mechanical protection is to protect against the PVC getting too hot in summer temperatures ! That's new !!

 

[elizabeth]

Hello Shobo,
glad to read your cables are vermin proof. We are thatched and very soon we will be having the loft cables protected too as required by our insurance. I’m not looking forward to the mess as it’s very very dusty up there. Once done, I think we will feel confident to lay down more insulation such as rock wool too, it will make a difference. Like you, I hope the lath and plaster ceiling will cope with the extra weight. I guess I’ll observe closely.

I just finished typing and read the above post about the cables being protected from summer heat - I’m surprised too. I need to ask my electrician some more questions from that comment.

 

[Abi Cott]

I believe the term your looking for is derating.

A shower in my last house was too high power for the cable technically. It was 9.5kw and running on a 6mm cable. However because it was surface run for its full length not buried in under plasterboard or passing through any insulated walls it was deemed safe.

It's not so much the summer heat as the heat generated by the electricity passing through it.

 

[shobo]

Thankyou Abi Cott / Elizabeth,

I appreciate the need to size cables. That wasn't where the electrician was coming from though. He looked at my cables and assured me that the reason for the metal covers is summer heat. The more I think about it, the more I think that is strange. Perhaps he meant summer heat and a simultaneous fault.

When the electricians do testing I am supposing they must satisfy themselves that cables are properly rated. Interestingly, one of the FP rated cables in my loft does feed an ensuite electric shower. I gather that in recent years, the standards on cable size for showers have been improved, cables now have to be thicker for a given shower wattage. I'll ask my electrician to examine my cables. I'm being very particular as to the electrics in my loft !!

At the same time, I am replacing an electric shower downstairs, and I have chosen a mixer shower rather than an electric shower because the existing cable would have had to be re-laid for a 10.8 kW shower. Doesn't affect the loft, though.

 

[Cubist]

Hello Shobo,
Always a good idea to insulate the loft-space but might I suggest you consider using Sheeps Wool rather than Rock Wool - same result but lower environmental impact.

A question for you and the wider community concerning the need to install metal cable trunking boxes in the loft-space. I've seen posts from several other members concerning this apparent demand being made during recent Electrical Installation Surveys. So far I have not found anything in Building Regs that demands this or explains any criteria associated with it. Does anyone know of, and can point me at, the relevant regulations or is this just another scam?

Cheers,
Cubist

 

[shobo]

Thankyou Cubist,

Where do I buy sheep wool ?

On the subject of metal covers for cables, where the requirement comes from ? Don't know. If I had an hour or two spare I might be able to find something. I've had a few electricians give me advice on my cottage. They haven't been consistent on this topic ! Most, but not all, say that the reason for protecting cables is to stop mice chewing. The one that said it is to prevent the effects of summer heat, also said its nothing to do with mice chewing ! Most say that FP cables don't need further protection, some say they do !

What they do have in common though is that they claim to go back to their office and look at the regulations !

I suspect that they are following guidance from NICEIC or whatever their trade body is, but that guidance is not fully understood and / or ill-informed, and that insurers have homed in on it and make similar conditions in their policies.

Maybe insurers have their own conferences and make their own conclusions as to what thatch owners must do.

The metal covers - I am not convinced, for various reasons.

However, and having witnessed an electric heater attached to a wall catch fire (not in this cottage), in my view, there is a case for insisting electrics are removed from thatched lofts altogether. But its not my strong view, because I'm a not actually doing it myself ! Not yet anyway.

Not able to answer your question sorry Cubist.

 

[MikeG]

........Always a good idea to insulate the loft-space but might I suggest you consider using Sheeps Wool rather than Rock Wool - same result but lower environmental impact..........

That is debatable. Sheep have a huge environmental impact. Most mineral wool insulation these days is made from recycled materials, and has the benefit of being A/ immune to insect attack and B/ not supplied by a company which shut down overnight and opened up under a slightly different name the following day to avoid the repercussions of failures in the insect proofing (leading to multiple such insect attacks in some very important buildings). I'd add C/ don't cost a fortune to that list, too.

 

[Cubist]

Hi Shobo,

Sheep Wool insulation is readily available through on-line suppliers; heres one link

https://www.google.com/url?sa=t&rct=j&q=&esrc=s&source=web&cd=1&cad=rja&uact=8&ved=2ahUKEwirmuCTu-jeAhXKI8AKHZBZAq0QFjAAegQICRAB&url=https%3A%2F%2Fwww.sheepwoolinsulation.com%2F&usg=AOvVaw1sFo1nJjkZGrwKCqOm7F9U

There are many others to be found with a quick Google search.

Thanks for your response to my question re BRs - looks like I need to wade through them again to get an answer - its two years to our next EI Inspection and I like to stay ahead of the scammers,

Cheers,
Cubist

 

[shobo]

I would add that the 'metal covers' that I have over my PVC cables, which get the unanimous approval of electricians, are NOT trunking or boxes. They are long flattish strips of soft metal which are bolted together, one on top of the cable, one beneath, forming a sandwich with the cable inbetween. They are very crude because at the ends, there is cable showing. Plenty for mice to get their teeth into, so if their purpose is to prevent mice attack, they could be next to useless. When I say this to an electrician, they say something like "but at least you've done something, so it passes".

 

[Flyfisher]

On the subject of metal covers for cables, where the requirement comes from ? Don't know. If I had an hour or two spare I might be able to find something. I've had a few electricians give me advice on my cottage. They haven't been consistent on this topic ! Most, but not all, say that the reason for protecting cables is to stop mice chewing. The one that said it is to prevent the effects of summer heat, also said its nothing to do with mice chewing ! Most say that FP cables don't need further protection, some say they do !

I don't really understand how covering cables with metal could prevent the effects of summer heat. Covering them with anything will reduce their ability to lose heat, which is the real issue as far as electrical design is concerned and the wiring regulations are pretty clear about 'de-rating' the current carrying capacity of cables depending on how they are installed. In general, cables simply clipped to a surface but in free air (ie not covered by anything) will have the highest current rating and any form of covering, whether metal protection or thermal insulation (or both) will require the cable to be de-rated to ensure it will not overheat.

Actually, I'd be surprised if covering the cables with insulation would push them beyond their safe operating capacity as far as the wiring regs are concerned, though it wouldn't be impossible. However, I would not be at all surprised if an insurance company used such a change to argue about any subsequent claim (assuming they found out of course). Such a situation would hopefully be easily avoided if the wiring installation was certified AFTER the insulation was installed. After that, different insurers seem to have differing demands when it comes to thatch, so if they require metal protection against vermin then so be it, but it should never be done in a way that could compromise the basic wiring regulations.

 

[livias]

MikeC wrote: That is debatable. Sheep have a huge environmental impact. Most mineral wool insulation these days is made from recycled materials, and has the benefit of being A/ immune to insect attack and B/ not supplied by a company which shut down overnight and opened up under a slightly different name the following day to avoid the repercussions of failures in the insect proofing (leading to multiple such insect attacks in some very important buildings). I'd add C/ don't cost a fortune to that list, too.

Interesting. I had heard mutters about sheepswool infestation but never any fact. Do you have any more info or links?

 

[MikeG]

Telegraph

Independent

The National Trust seem to have removed all mention of the problem, but 6 or 8 years ago they removed all the wool insulation from half a dozen properties when moth infestations occurred in at least one. I'll see if I can find anything in writing through a contact.

 

[tobydog]

Our thatched cottage is insulated with recycled plastic bottle rolls. It's an awkward space (can't stand up anywhere) but I ensured that, where possible, the cabling lays on top because of reports of potential overheating fire issues. The recently fitted high power cable to the electric shower is all clear of the insulation and the electrician made no comment about having it protected. Given how many thousands of houses have insulation laid by 'professionals' to meet energy efficiency targets, I'm sure there are thousands of miles of cabling sitting underneath insulation. Apart from showers, most of it is for light fittings / switches. We've switched the bathroom spots to LED.

We have been with NFU since we bough the cottage in 2009. They recently carried out a safety survey, including looking in the loft spaces, and made no mention about having wires encased to protect them from vermin. If we did have to have all the loft wiring protected, we would probably have to go for a re-wire because much of it in the loft runs diagonally and it isn't long enough to run it along the woodwork.

 

[Andys]

Well there's an article here where the sheepswool insulation became infested with moths, so I suppose it needs to be properly treated with insecticide ( but then it's not so 'natural' is it?)
From from the Independent, but it might be accurate:
https://www.independent.co.uk/news/uk/home-news/moth-infestation-wool-insulation-biblical-proportions-dream-house-eco-county-londonderry-northern-a7927761.html

Edit: Ah yes, just reloaded the thread to find I'm way behind the conversation and MikeG got there first.

I don't like the sound of retrofitted metal covers to make a kind of gappy conduit, I understand the cable thermal calculations are quite different for cables confined in conduits compared with those fixed to a surface in free air.

 

[shobo]

Thankyou Flyfisher. I'll ask my electrician his views on whether insulation could affect my certification. I could always ask him to re-test.

 

[skier-hughes]

I've had sheepswool insulation in my loft and some walls for around 10 years or so and not had a problem with it.