Building Regs tell us that fire stoppers are needed in ceilings designed to resist passage of fire.

I can't find any general case for typical UK 2 storey house (let's say it's detached) which define the former ceilings any more clearly.

I am talking retro-fit here, so no architect spec on the property.

Would the requirement for fire collars normally apply only to first floor/loft PB ceilings? - Or might it also apply to ground floor PB ceilings (given there is a huge fire hole already.. called a stairwell).

Or might fire stoppers (which cost a lot on top of an already expensive ducting bill) be not necessarily required at all by Building Regs in typical UK Domestic MVHR?

My install in a 2 storey new-build last year had a "fire rated" vent for the kitchen extract only

No idea what the regs say though but it was all approved

You can now get fire rated extract and supply valves, I bought one that had a collar thing that expanded in case of a fire. While they're not cheap, I'd still be inclined to fit one on every supply and extract valve on the ground floor, just for piece of mind.

I just had a word first with the nice lady at Dealec who was quite knowledgeable. She advises (naturally) that I'd need to ask my BCO, but when they specify systems for 2 storey domestic refurb, they normally add fire stoppers only to kitchen and (as good practice) to rooms with wood stoves. So that agrees with Tony. (& Also obviously to penetrations of integral garages).

For the record to help anyone else, I’ll add what I find from BCO if there is any more to add when I manage to get through.

BCOs all seem to misunderstand the purpose of these things and firehoods on lighting etc. too.
Ditto the various membranes required in walls but that's another matter.

The regs are all about maintaining integrity of exit routes from the building, not about stopping fires or things generally being fireproof.

So as far as I am aware the regs only actually require them to be installed where the duct/airflow would seriously compromise an exit route from the building. So passageways/corridors, hallways and stairs are particularly sensitive spots. Not compromising the integrity of a ceiling that may support an exit pathway or bedroom is also a good idea. You need to look at the route of the extract duct (which could deliver the fire to anything along it's route).

Still explaining the regs and questioning their purpose doesn't always get you anywhere useful. I am pretty stubborn though :-)

I suspect some BCOs are likely to just settle for seeing a fire blocker anywhere at all - so they can tick the box.

A thermal damper at the rear of the louvre will operate at anything above about 70C if you are luck and as high as 100+ C - that's whay the occupants will be dead - you couldn't survive the temperature at which the damper operates.

If it does close, then it will stop a fire in the room traversing into the dust and sperading elsewhere - it will do nothing for smoke incidentally - particularly "cool" smoke from a smouldering fire - so that gets deliveredpotentially to other rooms.

As the volume flow rates are so small in MVHR, it's quite possible that smoke will be deleived to rooms ratherthan extracted as the bounancy pressure of the hot gas overcmes the fan pressure of the MVHR.

Does your kitchen have a door - and does it have any kind of fire resistance ?

regards

Barney

That's interesting about the firehoods, etc.

We fitted fire rated downlights with acoustic firehoods for good measure. You seem to be saying that by the time a fire got going enough downstairs for the lights and hoods to be effective, we'd already be dead?

Dead from smoke inhalation?

What I was saying is that there is a certain contradicton in making a 2" hole in your ceiling fire rated, when the ceiling isn't - nor does it need to be.

Lots of tests have shown that the extent of penetration in a plasterboard ceiling has almost no impact on fire resistance and thus the impact on the rooms above.

Are your fire hoods of an intumescent type - at what temperature do they start to expand to fill the gap - how long does it take - is there a bloody great chimmney from ground to first floor (ie your stairwell) - will hot products of combustion hit the GF ceiling and spread sideways quickly - will that red hot gas layer thicken so it then flows through doorways - will it have a massive radiant component "shining" on persons in the room.

Will cooler products of combustion containing significant toxins spread equally as easily within the building without ever operating thermal dampers or intumescent materials.

How long do you expect to stay inside yor house in a fire situation.

My advice - buy a few good quality smoke detectors - make a plan, and if they go off , get out and stay out - everything else in a single compartment building is pretty pointless - and worse, leads to a misplaced sense of safety as you think they will be effective

Regards

Barney

Does anyone have a link to show how useless fire rated light or hoods are? When I try to google them I just get Advertisements or details on building regs?

I don't want to waste money fitting these things if they don't actually work.

Sorry, just realise that some questions were aimed at me. Will try to answer them as best I can.

Posted By: barneyAre your fire hoods of an intumescent type - at what temperature do they start to expand to fill the gap - how long does it take - is there a bloody great chimmney from ground to first floor (ie your stairwell) - will hot products of combustion hit the GF ceiling and spread sideways quickly - will that red hot gas layer thicken so it then flows through doorways - will it have a massive radiant component "shining" on persons in the room.

Will cooler products of combustion containing significant toxins spread equally as easily within the building without ever operating thermal dampers or intumescent materials.

How long do you expect to stay inside yor house in a fire situation.

The fire hoods are made from fire resistant material and have insulation inside to help with acoustics (rockwool?), the fire rated downlights may have intumescent material in them or they may just be fire resistant.
As well as the light fittings I also installed 100mm of acoustic rockwool between the ceiling joists, held in place by chicken wire before fitting 25mm thick Heraklith wood wool panels as a ceiling and plastering the lot with a thickish layer of lime plaster.
The house has a stairway in the corner of the building (opposite corner to where the kitchen is located) to the second floor that houses the living room and a bedroom with another stairway (located in a different place) that goes up to the top floor bedrooms. All rooms are self contained with doors that have self-closing hinges, so aren't open to the stairways.
I assume that in a fire that hot products of combustion would hit the ceiling.
I don't know if a red hot gas layer would thicken, but hopefully the doors would stop them it flowing through the doorways.
I don't know if the hot gas will have a radiant component shining at people.
Our house is made of stone and wood with most of the furnishings made from natural materials so I don't know if significant toxins would be released. With the self-closing doors I'm hoping they won't spread easily.
I expect to stay in my house as short a time as possible in a fire situation. I certainly won't linger!

I just spoke to my BC and after jumping all round part B for twenty minutes, and a discussion all round their office, he came to the conclusion that he would be looking for fire collars on all ground floor ceiling penetrations (to the first floor). Reason he gave was (Table 3 page 38) the duct is larger than 40mm and needs either boxing in with plasterboard or needs firestop.

The example I found on-line where one MVHR install company is using fire collars only in the first floor ceiling to the loft was (he observed), completely wrong. Likewise he firmly advised that my suggestion of kitchen only probably wouldn't wash.

So I should now either be very happy that I have covered myself, or disgruntled that I have incurred about £200 spend for multiple fire collars, when others wouldn't do it this way.

Barney
The ceiling/floor requires 30 minutes/60 minutes fire protection (depending on the building height), therefore is it sensible to stick a large hole through it.
As far as I can see this is a requirement within the documents, and fire collars should be installed.

@ Pile o Stone

try a google for an artice in the IEE Wiring Matters Spring 2005, writen by a guy called Bill Allen - that covers the impact of down lighters in domestic ceilings.

That would probably lead you to the tests undertaken by TRADA back in the late 90's to show the effect of a fire under a plasterboard ceiling, with unprotected openings, on the 30 minute resistance of the floor above.

Basically the report concluded the effect was negligible

Regards

barney

Well the report was focused on downlighters rather than MVHR louvres.

My point though, was that most domestic dwellings don't have any compartmentation (other than from each other). There may be a compartment line in a maisonette and for properties where the highest floor served is over 4.5m, or has a garage integral, but the bog basic, terrace, semi or detached two storey building is a single compartment - so adding all sorts of intumescent linings, thermal dampers, fire rated downlighters etc etc is a complete and utter waste of time.

Just install smoke detection and have opening windows upstairs - job done. If BCO tell you differently, then challenge them

Regards

barney

I think that might have been my conclusion, yes.

How that stacks up against a manufactured joist is the subject for other tests but I would suggest that performance wouldn't be dissimilar

regards

Barney

Hi Barney, I believe your sage sounding advice more deeply than BC. However I feel like the pawn now in this one, not having expert background in fire safety. (Perhaps I would have lived more happily in ignorance).

But I came across this one, which seems to concur with BC: http://www.nhbc.co.uk/Builders/ProductsandServices/BuildingControl/documents/filedownload,40528,en.pdf

The article makes the same argument as BCO that when ducts continue through to upper storey they would require protection.

By my way of thinking using that argument, if MVHR were downstairs, and atmospheric ducts were in the roof, collars would be needed on ducts to first floor and atmospheric ducts. (potentially four collars depending on air distribution detail).

If MVHR were in a loft space, technically only two ducts might (depending on the air distribution detail) penetrate right through, but since these two main fresh/stale ducts wouldn't penetrate the PB ceiling of ground floor, they remain in the first floor void (under the floorbopards). Implication is that every room vent to ground floor connected in to these (and hence directly to the upper storey) would need a collar.