jack

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!

Good to see that confirmed. I'm sure I saw one that was only for use in brickwork - obviously a different beastie to this. Yes, this was the bit that concerned me. I suppose that at the sorts of temps required to activate the intumescent material, a semi-rigid MVHR duct should be soft enough to be squashed closed by it.

One of our smoke/heat alarms (Kidde brand, I believe) is mounted to this optional pattress that contains a relay. When any of the alarms is triggered - they're all linked to each other, per building regs - the relay is tripped. We have it wired into our home automation system and I'll eventually use it as a trigger to send us an email and/or text if we're out and the alarm goes off. It could also be used to close a volt-free contact on an MVHR, or as a control signal to a relay that does the same. Re intumescent seals, I think you need a special type of pipe that can be crushed by the intumescent material, plus it needs to be surrounded by brickwork if I remember correctly. I've seen MVHR inlets with an internal intumescent closure or collar that operate in a similar way - might be a simpler route to this functionality?

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

Git

We used recycled crushed concrete for our 45m long driveway, which came in all sizes from fines to something approaching half brick size. It wore remarkably well for 18 months and is now a base for our gravel driveway. Do you need it to be permeable (eg, to meet SUDS requirements?) You should also put a geotextile membrane down to prevent migration of the new layer into the ground beneath.

Well done. The price you paid should have gotten you a highly competent piece of design work (the cost was more than a full day's work for most trades, even in the south east). Stick to your guns and let us know how you get on.

Interesting. Would you call foil-faced PIR "foil insulation"? If so, I think even this carefully worded bit of misdirection is arguably inaccurate!

We still have some cladding to do (eaves) and I think we'll just scrape by with our 10% over estimate.

Personally, I'd keep the MVHR within the heated area to avoid potential condensation issues. I can live with a little bit of condensation in the external ductwork. I'm less happy with the prospect of condensation within the MVHR unit itself, mainly for the longevity of the electronics and fan bearings etc. The actual difference in heat loss between the two scenarios will be difficult to quantify. The performance of an MVHR unit is hit surprisingly hard by the length of uninsulated external ductwork coming into the heated area of the house (for an internal MVHR - vice versa if it's outside). The unit itself will also contribute some losses, but I suspect you'd need to know the exact makeup of the interior MVHR insulation relative to the duct paths to understand whether internal or external mounting will give higher losses. This is because the one side of the MVHR is at the external temp and the other is at the internal. When it's very cold outside, there's a big temperature difference between these two, and it's hard to model how the unit as a whole will act in terms of heat transfer. I suppose you could negate this issue by heavily insulating the unit itself.

I don't think you want to remove it. Saturating it could work, although awkward to get to it before the walls come down (be a bit time consuming drilling holes for a hose or spraying water in through top of cavity if you can get to it). I'm not familiar with cotton insulation, but assuming it's a bulk product like batts, it'll likely be clumped together pretty well given how long it's been in the cavity. Can you knock a hole in a wall somewhere and see what state it's in?

How expensive is "incredibly"? Our (Siberian, Russwood-supplied) larch has been up about a year and is so far weathering pretty unevenly in places. As you say, underneath overhangs has hardly weathered at all, plus we have places where there's uneven staining from water movement. It'll mostly even out in the end I suppose/hope. In the meantime, I just tell myself that wood is a natural product and this is how natural products behave. Sioo wasn't available when we needed our larch, although even with what we're experiencing now I'm not sure whether I'd have used it. The uniformity is very nice, but I do wonder whether there's a loss of longer term character compared to letting it weather naturally (with all the flaws that that might bring).

I've generally got a pretty good memory, but within a few weeks of putting plasterboard up, I'd completely forgotten where just about everything was routed. Even though we took several photos of every wall before boarding, we've still had one or two situations where a crucial angle is missing and we've had to dig around.

Ours was around £7k to knock down and remove a small bungalow and detached concrete prefab garage in Hampshire/Surrey borders, including disposal of (low risk) asbestos floor tiles. That was the cheapest quote by some way - wouldn't have taken it if we hadn't had a recommendation from someone else who'd used them.

If you paid by debit card rather than bank transfer, you may still be protected: http://www.moneysavingexpert.com/shopping/visa-mastercard-chargeback They don't listen to self-builders, but they might listen to a bank.

Ouch. Really sorry to hear this. Things inevitably go wrong when building. The real difference is when suppliers acknowledge their cock-ups and do what needs to be done to rectify them. Did you pay by credit card?

Not on that clay it wasn't (well, maybe in a wet year!)

A guy we had do some building work for us is working on his own extension to a Victorian house. He's just learned that the building inspector wants 3m deep footings due to the soil he's on. He pointed out that the Victorian house has one foot deep footings and is still standing without cracks 100+ years later. Oh, and he has no access for even a mini digger, so all has to be dug by hand (which I guess the Victorians did too!)

Yep. We briefly spoke to a German architect at a building show once, and as soon as we mentioned a plant room he got very excited and started verbally laying out a basement for this and all the other stuff you list above. We backed away slowly. He's still there talking about it for all I know.

Yes, to be avoided unless accessible for servicing.

One of our smoke alarm mounts has a relay that closes when any of the alarms is triggered. Our home automation system takes this as an input and... presently does precisely nothing with it! But we could use it to kill power to the MVHR if desired (and wired). Personally I don't think it's an issue - building regs don't require it and I can see arguments both ways for leaving it on and turning it off. For me the main thing is waking up and getting the flock out of the house as soon as there's smouldering. By the time any fire has got the bit between its teeth, my family and I will be long gone.

If that happens, then I imagine the pressure would completely overwhelm the MVHR fans. If you're right about pressure, then closing the inlet at this point will cause a further increase in pressure, and the smoke will therefore potentially work its way through the rest of the house seeking further exit routes as the outlet in the area of the fire (most likely the kitchen) is overwhelmed by the volume of exiting gases. I know you asked how you can achieve your proposal. I think Pete's offered one option there. But turning off the MVHR (the standard proposed approach) will do most of what you're asking. You've said that pressure increases greatly. If that's right, then nothing the MVHR does is going to make much of a difference. I'm not saying any of this is fact, because I simply don't have the necessary knowledge to do so. There are some interesting principles at play though, and I suspect there must be a reason that MVHR manufacturers recommend simply turning off the MVHR in the event of fire.

Allowed by whom? That's a good question! Our (private) building control has seen our plans including the UFH being clipped to the steels. He's happy. Several other people have had MBC houses (which all use this arrangement) signed off by building control. I believe @Bitpipe had an architect (or perhaps engineer) who wasn't comfortable with this approach, but this was in a basement with some very stringent structural requirements. Don't suppose the steel would hurt heat movement, but bear in mind that with a very well insulated slab you don't tend to use high heat levels. Our ASHP is programmed to provide 25 deg C water to the slab during winter. I programmed in a mild weather compensation curve starting at 10 deg C exterior temp, with the ASHP supplying up to 28 deg C water at a -5 deg C exterior temperature. Never felt cold all last winter. You basically keep the slab largely at the same temperature all day and night, rather than blasting heat in morning and evening like with a screed.

I looked at this before we started looking at raft foundations. I recall it being interesting stuff, but very expensive. I think it's produced somewhere in Scandinavia.