Fri, 24 May 2013 22:35:59 +0100 http://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150615#Comment_150615 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150615#Comment_150615 Thu, 05 Jul 2012 13:07:13 +0100 thornewyness
I am thinking of incorporating a passive house detail for MVHR extract using a transfer gap behind the architrave at the head of the door. Will this work for fire regs with an expanding fire seal, or will intumescent seals hamper the ventilation required? Has anyone any experience?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150662#Comment_150662 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150662#Comment_150662 Thu, 05 Jul 2012 21:02:11 +0100 GaryB Transfer gaps work fine and the intumescent strips aren't a problem as they don't seal until high temperatures are experienced.
It is surprising just how much ventilation can pass through the gaps around a door. A standard door can pass 70 litres/sec at a pressure differential of 15 Pa.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150666#Comment_150666 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150666#Comment_150666 Thu, 05 Jul 2012 21:47:08 +0100 tony http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150685#Comment_150685 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150685#Comment_150685 Fri, 06 Jul 2012 08:33:47 +0100 davidfreeborough Posted By: tonySounds like a bad idea to me, is it for ventilation or draughts?I think he's talking about internal doors & maintaining MVHR driven circulation when they are closed.

David]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150687#Comment_150687 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150687#Comment_150687 Fri, 06 Jul 2012 08:37:01 +0100 tony http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150696#Comment_150696 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150696#Comment_150696 Fri, 06 Jul 2012 09:52:53 +0100 Ed Davies Posted By: GaryBA standard door can pass 70 litres/sec at a pressure differential of 15 Pa.
Interesting and worth knowing but note that 15 Pa is a lot. 2 m × 0.75 m × 15 Pa = 22.5 N which means the force needed on the handle when opening or closing the door would be about the weight of a 1 kg thing¹. That'd be very noticeable. Also, those conditions would dissipate a fraction over 1 W, probably mostly as noise - energy which would have to come from the fans.

How does flow rate scale with pressure difference - I've a feeling it's either with the square or the square root but can't work out which?

¹ The door's a lever, the other half of the pressure being taken by the hinges.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150774#Comment_150774 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150774#Comment_150774 Fri, 06 Jul 2012 21:54:38 +0100 GaryB Operating theatres and clean rooms are designed to 25-30 Pa to keep bacteria and dust out, so 15 Pa is not a lot of pressure, but pressurised ventilation would be rare in a domestic setting. Pressurised fire escape corridors and stairs go as high as 50 Pa. Above 50 Pa it becomes difficult to open the doors!]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150887#Comment_150887 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150887#Comment_150887 Sat, 07 Jul 2012 23:40:51 +0100 djh Posted By: tonyI leave a gap at the bottom of the door for that!
But then it wouldn't be a fire door, which is the point of the intumescent seal?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150890#Comment_150890 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150890#Comment_150890 Sat, 07 Jul 2012 23:55:16 +0100 tony http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150913#Comment_150913 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150913#Comment_150913 Sun, 08 Jul 2012 10:02:51 +0100 Ed Davies http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150918#Comment_150918 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150918#Comment_150918 Sun, 08 Jul 2012 10:16:24 +0100 Joiner
Once the intumescent strip has sealed the three edges and effectively sealed the room, then smoke will rapidly build up and in very short order find its way under the door.

If that's the situation created by a MVHR system then it's lunacy.

If each room can't be treated on an individual basis by the MVHR then it shouldn't be fitted if it means compromising the integrity of a fire door.

(I can't get hold of my fire officer son at the moment, but as soon as I do I'll ask him what he'd do if he saw a situation like the one being recommended here.)]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150925#Comment_150925 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150925#Comment_150925 Sun, 08 Jul 2012 10:46:54 +0100 GaryB
An MVHR slightly pressurises the habitable rooms which could help keep smoke out.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150942#Comment_150942 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150942#Comment_150942 Sun, 08 Jul 2012 12:33:18 +0100 Joiner ]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150951#Comment_150951 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150951#Comment_150951 Sun, 08 Jul 2012 13:52:16 +0100 GaryB
It was Tony suggested undercutting the doors, not me!

I was pointing out the level of leakage possible through internal doors even those which appear to be a tight fit.

It is also my understanding that fire rated doors are rebated and fitted with intumescent strips on the bottom regardless of whether undercut or not.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150953#Comment_150953 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150953#Comment_150953 Sun, 08 Jul 2012 13:54:35 +0100 tony http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150963#Comment_150963 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=150963#Comment_150963 Sun, 08 Jul 2012 15:05:23 +0100 Joiner

HOWEVER

Just spoken to fire officer son (fresh in the pub after a morning's diving) and he says no formal checks are done now by fire officers unless there is a statutory requirement, in a residential home or hotel, or such like, so apologies to Tony. He did say that any gap under a fire door has to be "a sensible one of about 6mm" because it's assumed that smoke will probably not drop to that level within the room in which the fire is happening. He'll check with the enforcement officer tomorrow and get back to me if there is such a thing as a recommended maximum gap.

I wonder why no one makes anything like this to be 'triggered' by heat in the way of intumescent strip?

http://www.norsound.co.uk/Door-Bottom-Seals/]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151059#Comment_151059 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151059#Comment_151059 Mon, 09 Jul 2012 15:37:02 +0100 djh
(1) don't they increase noise transmission?

(2) they would allow small animals (I'm think of mice that the cat has brought in) to escape underneath, which is not usually desirable.

So I'm interested in any alternatives.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151135#Comment_151135 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151135#Comment_151135 Tue, 10 Jul 2012 09:16:10 +0100 Joiner
Just texted my son and he says he's hoping to hear back from his enforcement officer colleague later today about whether there's a recommended max gap allowable as far as the fire service is concerned.

He did say in that earlier conversation that if he ever saw a gap under a door that he thought "a bit wide" he'd advise against it "for safety's sake", but that at the end of the day, as far as any prescriptive regulations went, it was down to the householder concerned to worry about the safety of his or her family.

I'd personally be concerned for the simple reason that if you're cutting a slice off the bottom of a door to allow an easier movement of air between rooms, then it surely goes without saying that if that air contains combustion smoke it's going to be shifting that around as well, courtesy of the MV air changes.

What am I missing here?]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151152#Comment_151152 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151152#Comment_151152 Tue, 10 Jul 2012 11:18:00 +0100 RobinB Posted By: GaryBIf the door is fire rated then it should have intumescent strips rebated into the bottom of the door as well.

It makes sense but I've never seen it or been asked for it in a domestic setting.

But how else do could we fit MVHR in a house which requires internal fire doors -I suspect the relatively small air-flow just pass through the small gaps that the intumescent strips would fill in the event of fire.

Our fire doors are generally only ever closed at night.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151158#Comment_151158 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151158#Comment_151158 Tue, 10 Jul 2012 11:32:52 +0100 Ed Davies http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151177#Comment_151177 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151177#Comment_151177 Tue, 10 Jul 2012 14:12:21 +0100 Joiner
Apparently, they're easy on refurbs of old houses because of the difficulty of finding a doorway in square and plumb.

But his colleague knew nothing about the trend for MVHR and asked that I send him a link to the forum so that if there is "reason for concern" he can advise region and apprize them of the technology so that they can assess the trend for risks they should be aware of, if there is then they'll pass it on to national level and "something will have to be done" to get BC involved.

Hmmm.

I did mention intumescent strips, and even the heat-activated duct valves, but of course it isn't the heat that kills, necessarily, it's the SMOKE, and that doesn't trigger intumescent anything.

I'm still a wee bit concerned for all the reasons I outlined in my previous post.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151185#Comment_151185 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151185#Comment_151185 Tue, 10 Jul 2012 15:01:00 +0100 TimSmall
I was thinking of tying my domestic MVHR system into the fire-alarm system to do something similar... In an MVHR system which I installed 8-or-so years ago, I stuck a heat-closing (70 degree C?) vent port in the kitchen - since the duct run then passed through a bedroom on it's way to the MVHR unit.]]> http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151810#Comment_151810 http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=9298&Focus=151810#Comment_151810 Mon, 16 Jul 2012 16:22:55 +0100 Joiner
"General requirements for mechanical extract ventilation - Mechanical ventilation to rooms without openable windows to be linked to light operation and have 15 minutes overrun and a 10mm gap under the door for air supply." (p.41)

http://www.fdean.gov.uk/media/Assets/Planning-BC/documents/approved%20documents/NEW_DWELLINGS_GUIDANCE_EDITION_5.pdf]]>