Airtight electrical back boxes

[tew1]

Hi, I'm not sure if anyone will have an answer, but I'm doing some research into airtight construction using timber frame (e.g. on the interior of the timber studs, there is an airtight plastic membrane, taped at all corners, with fresh air brought into the structure using a mechanical heat recovery system). Obviously, socket and switch outlets can be a major source of air movement. In the US and Germany, you can get specialist airtight backboxes, which are side mounted to the studs and have a rubber seal around the cable entry and plasterboard hole. Do these exist in the UK? I can't even find side mount boxes in the UK (only the plastic type that goes in a hole in the plasterboard).
Any ideas? This is the same case with insulated airtight recessed lights (suitable for covering with insulation). They are widely available in the US, but don't seem to exist in the UK

Untitled

• tew1
• 10 Feb 2014
• 1

Untitled

• tew1
• 10 Feb 2014
• 1

 

[RF Lighting]

There is currently nothing on the market which will do what you want. I guess you could just wrap a standard box with aluminium foil tape as used by plumbers for sealing flues?

You can get airtight downlights, but you'll probably need to look for bathroom fittings designed to prevent the passage of moisture into the loft space.

 

[PrenticeBoyofDerry]

Spotted these
http://www.schneider-electric.com/p...l/2630-flush-mounted-boxes/2256-multifix-air/
But never had the pleasure!

 

[RF Lighting]

Are those designed for UK accessories?

 

[PrenticeBoyofDerry]

Just spent a little time looking at the spec and unfortunately seems not, which is a damn shame as they look like they could do the job!

 

[tew1]

I can't believe there is no product for achieving an airtight seal around plug sockets and switches, or even for mounting boxes onto the side of wall studs. Major gap in the market. What do people do in airtight homes? Do they just slop silicon around and hope for the best?

 

[EFLImpudence]

What do people do in airtight homes?

.
Suffocate

 

[tew1]

.
Suffocate

MVHR

 

[ekmdgrf]

I can't believe there is no product for achieving an airtight seal around plug sockets and switches, or even for mounting boxes onto the side of wall studs. Major gap in the market. What do people do in airtight homes? Do they just slop silicon around and hope for the best?

Get yourself on Dragon's Den

 

[bernardgreen]

.
Suffocate

MVHR

And when the power supply fails and there is no MVHR they do suffer.

The money saved in reduced heating of an "air tight" home is likely to be spent on treatment of the ill health that seems to come when living in an air tight buiiding

 

[ekmdgrf]

And when the power supply fails and there is no MVHR they do suffer.

The money saved in reduced heating of an "air tight" home is likely to be spent on treatment of the ill health that seems to come when living in an air tight buiiding

I wouldn't like to form an opinion on MVHR as it's the first I've heard of it. Couple of points of order though:

Point 1: What really are the chances of it being affected by a power failure? A house without power is fairly unliveable even without MVHR. If it's that much of a concern, I would imagine that a MVHR budget would notice having a battery/genny tacked onto the end of it.

Point 2: Healthcare is free at the point of use in the UK.

 

[tew1]

MVHR is very common, and is used in most new builds which aim to reach the highest standards of energy efficiency. You get better ventilation than most conventionally ventilated homes, without any heat loss, you can also combine it with ducted heat, as conventional radiators are not required in airtight homes-you'd boil! and there's no thermal mass. No extractor fans or trickle vents except for the kitchen hood, and tumble dryers must be in a cold room with a vent to the outside. If the power goes out, enough air will trickle in through the ductwork naturally. It's curious that there are no products to achieve seals around all the hundreds of sockets and switches you have in a structure, seeing as even a small opening like a letter box or gap around a door can become a major source of heat loss in an airtight home.

 

[viewer]

If it was my research, I'd start by testing just how much air would get through a normal socket or switch. These are on internal walls with insulation between inner and outer leaves and cannot be compared with letter boxes or gaps to the external air. Those gaps introduce cold air which needs heating, so the heat loss is to this air. The introduction is due to pressure differences which should not affect a socket or switch cut into the leaf. Electrical cables are no longer run into cavities, but are kept inside the inner leaf.
It might be very interesting to look at variations in pressures from the MVHR system (normally assumed to be overall zero) and see if there is any benefit from slightly higher over pressure. This commonly done in sterile environments and food manufacture so reduction in dust, spores, etc might be feasible.

 

[skenk]

I have fitted sockets in walls with a plastic membrane behind the plasterboard, just take care not to pierce the membrane.

Found these on google, they look like a pita though, you will need deep back boxes i expect http://www.safelincs.co.uk/astroflame-intumescent-socket-box-insert/#ProductReviews

As for side mounting to timber studs... some metal back boxes have screw holes in the side, or else you can drill your own in the back box.

 

[tew1]

The positive pressure idea is interesting, this is used in offices and commercial buildings, often where heat is supplied through ductwork to avoid drafts.
I'm talking about sockets and switches in the plasterboard penetrating the vapor barrier on external timber framed walls. I've experienced first hand how big a problem it is, especially in an instance where a thermostat had cold air blowing through it from the back box, causing the room to constantly overheat. A 50mm service void can negate this problem, but this is unconventional and means all cables would have to run vertically only, ideally the cables run through the studs, deep enough to avoid damage from nails e.t.c. and a 50mm void causes huge problems finding studs for hanging shelves/TV's e.t.c.