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I agree Terry. In addition, what little guidance can be found from the MVHR manufacturers seems to suggest fire-closing extracts in the kitchen, and switching off the MVHR in the case of a fire. If you follow that advice and meet building regulations, I can't see why an insurer wouldn't pay up. Indeed, departing from that approach (which, Warby, I respectfully think you are risking when you propose boosting during a fire) seems more likely to raise question marks with an insurer. If insurance is of concern, the safest thing is to ask two or three insurers for their written recommendations, or better yet get their written approval of what you propose to do. If you follow that, they can hardly complain!

Martin, the purpose of an MVHR is mechanically ventilate a reasonably airtight house whilst retaining the heat that would otherwise be dumped during ventilation. Most MVHRs can recycle the whole house volume in 2 hours but will normally be on tick-over doing so perhaps every 4 hours. This is perfectly adequate to keep the house fresh and moisture-free. It is not designed to perform emergency smoke dumping. As Dave says, the BRs now give other guidance and escape routes and means of clearing smoke. I feel that you are using the wrong tool to address a very real issue. After having thought about this, so long as the MVHR shuts down and any ducting channels are properly protected it should not worsen the fire risks. My parents lived well into to their 90s and my mother had increasing dementia for the last 10 years of her life; towards the end neither was capable of standing after a fall. Both had emergency call buttons around their necks and we encouraged (with minimal success) my father to carry his mobile on him at all times. We and social services made a number of modifications to their house to enable them to continue to live in it and in my father's case until his terminal admission to hospital. Yes fire is a risk and the outcome might be frightful, but so is simply lying on a floor unable to move or regain standing, and slowly freezing to death or starving. You must live in a dwelling matched to your capabilities, and whether you have MVHR or not really isn't a material factor in this judgement. So for example in such cases any smoke detectors should be automatically link to an alarm systems and included in response scenarios. My answer is simple: I believe that it will make no difference, if the house is built to current BRs and correctly maintained. There are other risk factors for fire that are far more material, for example does the house have open fires or do the occupants smoke? And for example a house fitted with MVHR almost certainly won't have open fires.

Building regulations now prevent you from having locking windows to escape routes (bedroom windows for example) So that would not now happen. Although not a building regulation, I would not have entrance doors that need a key to open them from inside. I also point out that wiring regulations now require that cables above exit passages must be supported by non metalic means to prevent firefighters getting entangled by drooping cables. Also, related to the melting point of ducting. Do you think with a full fire raging, and the melting point of PVC cable, that the power feed to the mvhr will still be on and working for very long after a fire starts? Perhaps we should all wire smoke alarms and mvhr feeds in MICC cable which is about the only thing that would last any length of time in a fire.

I think we have been spared this in glorious Scotia *hopes he does* since we have an abundance of the wet stuff. In the future I see Victorian scale infrastructure projects pumping fresh highland water to the south in exchange for tariff free imports of fine crockery complete with images of young George the cute. Water may well be the new oil..I'm serious???

Externally you've got no problems. Distance between IC's is between 40 - 90m allowable. I would just make sure all the points are rod-able, especially at the base of the stack. I though the length of branches was limited to 3m for a 40mm pipe although this might only be without an additional AAV (see attached). Although I've just installed an internal shower waste which is around 5 ish meters to the hopper and no problems yet.

Having taken the time to read the relevant building regs document (G?), I am a little doubtful about its efficacy.. My initial impressions are: 1 - The model and calculations suggested are only tangentially related to actual water usage in the future. 2 - The calculator looks like a over complicated, mainly disfunctional, zombified hangover from the Code for Sustainable Homes, and like the CFSH requires certain decisions to be made at a time which is not sensible - for example it makes the rating of your house dependent on the type of washing machine you choose to install. (rant) That is simply stupid, and is founded in a politico-bureaucratic regulatory desire for micro-control of our lives which has been pushed beyond the realistic. I don't want to make this political, but our Govt in the 2000s did have an addiction to microcontrol, checkboxes and "Tractor Statistics"; that poison has not yet been rooted out sufficiently. (/rant) 3 - The model admits that it cannot be an effective measure of future water usage. 4 - The relationship between consumption and occupancy is not clear. ie If you tell them there will be 3 not 2 people living in the house, does it help? 5 - I can see some sense in eg limitation of flow rate of a tap, use of aerating fixtures etc, basic limitation of washer use per kg of washing, but they have gone too far in their desire for control. However, it is in the regs, and with the regs we are required to comply, so 1 - I think a brief conversation (email: you get a written record) with Building Control is indicated to find out if they have adopted locally the tighter option. 2 - The easy way is to take The Red Pill - which is a "fittings approach", if you can meet the limits. It may be worth fitting cheap, compliant items, and replacing later rather than enter the nether world of the Water Efficiency Calculator. 3 - If you take The Blue Pill, then I think the way will be to have a Water Efficiency Calculator spreadsheet (which must be available somewhere), and keep it as a living document during the relevant stages of your design. 4 - Take care on the amount of detail you give to official people. The process looks flexible enough that you can adjust what you do to meet the requirements in several ways. Not sure how you would get one of those two person "Gent plus Geisha" Japanese wooden baths with seats past the "185 litre to overflow" limit, though - perhaps a complaint against the regs to the Equalities Commission on the basis of Race Discrimination. Or include two overflows, the lower one fitted with a cork. Ferdinand

There is a further option for 1 and 2 which I haven't discussed, and that is to have 2 narrow ensuites back to back - which I assume is what @Nickfromwales is implying by 2 windows. If pushed, an ensuite shower / loo / whb can be fitting into around 0.8x1.8m or 1.0x1.4m, which would let you do 2 back to back in the space you have or a little more generously in the space with a little extra nicked from the bedrooms, and have more left over for something else. An example of a not particularly compact example is here: http://ukbathroomguru.com/adding-a-small-en-suite-shower-room/ These are 2 links you may find useful: Plans: http://www.houseplanshelper.com/small-bathroom-floor-plans.html Rules: http://www.houseplanshelper.com/bathroom-dimensions.html Also lots on Pinterest but they spam you to register. I have an Ikea whb called a Lillangen, which is 400 deep and 600 wide, with a "stand things here" build-in shelf behind the bowl and vanity unit for about £200 iirc. Good but needs effort to keep clean (wipe every day). The extra width prevents it feeling mean and it is the right shape for cleaning boots. http://www.ikea.com/gb/en/catalog/products/00135419/#/30135432 But there are plenty of options about. Just take the time to let the concept steep in your head. There is also a thread on ebuild about thin partition wall construction, where amongst others Jeremy talked about his compact walk-in-wardrobe. Photos are inaccessible but that wouid be a good thread for someone to move over (you know you want to). You could get your partition wall down to 60mm thick or so. http://www.ebuild.co.uk/topic/14367-building-a-thin-partition-wall-how-thin-can-i-go/ If you could take your space depth up to 1900mm or 2000mm between the two rooms, you could even plan a 1.8mx0.8m to 2.0m x 1m shower ensuite each side (760mm x 1m shower inside side with no door and shower head on bedroom wall to avoid splash (*), whb facing, loo against external wall with window - big mirror above the whb facing the sliding (?) door to make it feel larger), and then leave space for a 1.5m x 900 deep L-shaped "stand in" wardrobe for each room, with storage at the back and the side. You then need to work out how to get it past the regulators :-). (Update: you *could* look at ensuite pods, which could simplify your construction, as used in student accommodation etc - from a couple of thousand each. Suspect most here won't go for that option, though - too easy! ) Ferdinand (*) I hate moving doors on showers.

I used Marmox Thermoblocks under my sole plate. Also ££ but I think may have been slightly cheaper. I did end up going to Belgium as local merchant (Jewson) messed me around with supply of the size I was after. Worth checking on lead times and don't believe anything your merchants tell you - go direct to manufacturer for confirmation on UK stock. Blocks were easy to lay and nice and light to carry around. And should help protect the sole plate.

Hi Terry I am not sure what your answer would be concerning protection of the fabric of the building. You mention stopping fire escaping out of a sealed room which really depends which way you look at it. Firstly we would always say close the door to a room on fire to limit smoke travel to aid people trapped in the building to travel to a place of safety in a smoke free atmosphere. When you do this this accelerates the ferocity of the fire as the room heats up very quickly and thus all items inside that room reach their critical temperature to spontaneously ignite.From your point of view it would be better to leave the door open (assuming everybody out of the building) to give more time for the Fire Service to arrive (more smoke damage) and the fire would not be at such a critical stage but this is not an exact science and there are so many different factors that are out of your control. Apart from fitting fire resisting plasterboard or even doubling up and being really thorough at fire stopping which would give you well over an hour of protection and then concentrate on early detection with a link to you via a mobile to inform you of a fire. What about installing some sort of cctv that could relay pictures of the rooms in your house if you are away or even temperature sensors in the ceilings to enable as early detection as possible. All of these are relying on home automation of some description and my knowledge of such systems is better left to other people on this forum. The other possibility is fitting a misting system which works out at about £2000 for an average 3 bedroom house. The only problem with this is they usually only cover the escape corridor to enable people to get out where as you would probably want whole house protection which could work out quite expensive. This price is for one pump and mister, tank and battery back up in case of mains power failure. The only other option is to build as fire safety conscious as you seem to be doing and hope you never experience the horrors of a fire in your home. Get as good an insurance policy as you can and let the insurance company re-build your house.

The original question was about shutting down certain MVHR vents and turning on full boost in the event of a fire. We've drifted a bit from that so I think it would be useful to briefly summarise the thread for those who might find it in the future. It seems that best practice for what to do with an MVHR system in the event of a fire is still developing in the UK, presumably because building regs haven't yet caught up with the increasing use of such systems. One thing several posters seem to agree on is that MVHR inlets and outlets should ideally be closed when a fire is detected. There also appears to be some consensus that shutting off the MVHR in the event of a fire is useful. As far as anyone who posted on the thread knows, building regulations do not seem to require either of these actions to be taken, nor do they require full boost in the event of a fire as was mentioned as desirable in the original post. There also seems to be a consensus that getting people out should be the first priority where there is a fire. To help keep this information together, I note there's also a broader discussion of fire regulations (including some input in relation to MVHR) here: Many thanks

With regards to the MVHR, shutting it off in the event of a fire could easily be done with an external emergency stop switch, or some sort of relay wired in to the smoke alarms to switch off the MVHR while they are sounding. There are also plenty of intumescent seals available for pipes, which clamp round the outside, and crush the pipe and seal the hole when the temperature raises above 180 degress which would all go towards stopping the spread of fire.

i have read with interest all of the thoughts on fire in buildings, with or without MVHR and how people seem to want to overcome this issue. Basically I can assure you that all you need to worry about is early detection and getting out of the building. People have mentioned using fire blankets and extinguishers as a means to preventing the fire getting worse and giving more time to evacuate. All I can say is that unless you have been trained to use either the blanket or extinguisher you are not only putting yourself at risk but can create a rescue situation when there would not have been one if you had just left the building. I am a retired Firefighter and if I had a penny for the amount of people who assured me they could use a fire blanket and when I asked them to show me they would have ended up in hospital with severe burns to their hands, Same goes for using an extinguisher, even with the best will in the world you can turn a small fire that could be contained by just shutting the door if you can safely and getting out of the building or seriously spreading the fire by mis direction/application of the extinguisher. The UK Fire service now use a portable fan to fight fires in buildings but the precautions they have to undertake to ensure that the fire is not spread around the building is quite an an art form. Basically they seal the doorway with a large fan placed externally and wait until a team of firefighters go inside to ascertain the room that contains the fire, close all doorways to other rooms, open the door to the room with the fire and create an opening usually by breaking a window in that room They must ensure they have a jet on the exterior of the building to stop fire spread up the outside of the building and then once all that is done they turn the fan on which dramatically reduces the heat in the building and pushes all the hot gases and smoke out of the window. The reason they do this is to make their working environment easier and aid any trapped people who might still be inside the building. As far as I can see what would be beneficial is for some sort of damper/ shutter that closed in the ceiling/wall vents so in the event of fire the MVHR trunking does not allow smoke/fire to travel to other rooms/floors and turn the MVHR off as you would not believe how fast a fire can travel if the only source of oxygen is coming from the MVHR unit, especially in a Passive house. I still think early detection is what you need to ensure to enable you to get out and always have a plan as to what you are going to do as a family in case of fire in the house.It is imperative that if you have young children then you understand who is getting the children from their bedroom (fires predominantly at night), who is calling the fire service and if you cannot get out what room you need to go to to enable you to maybe escape out of the window or make it easier for the fire service to rescue you. .