Mike

From the ventilation aspect, provided you make provision to do 2 later, you could try 1 to start with and see how it goes. However from the fire control perspective it may be advisable / you may be required to have a ceiling, which is what I'd do anyway.

A very useful clarification, and if the aircon can handle the excess heat that's also very good. I'd say that was much less of a concern than with a separate external extract. The MVHR's extract fan will need to work a little harder as the air flow through extract vent in the cabinet goes into reverse & more has to be pulled through the other extract vents, but a Zehnder is doubtless clever enough to adjust for that automatically. I agree :)

That ticks off everything I mentioned above. So most likely a major part of the solution is to replace the extractor fan, boost the room temperature, and leave the eves cupboard doors open. And apply some mould killer. It seems unlikely that the damp is coming through the roof (if that's what you're thinking the damp proofing would help), so probably not. But maybe I've misunderstood. As you're sure it's all built OK as above, I don't think that's likely to help.

Good question! It may be useful in the heating season (not necessarily, if the building is already heated enough), but the problem is handling it. The heat's generated in a confined space, which will rapidly heat up. As per the calculation above, I reckon that would mean extracting in the region of 161m³/hr of air from that one cabinet. Maybe the MVHR could add that much extract in boost mode, but that would boost extract from all over the house, which would tend to push up heat loss overall, while not extracting anything like enough from that one cabinet. So it becomes complicated...

If it's a breathable membrane installed in accordance with the manufacturer's recommendations / the BBA certificate, and the conversion was done to Building Regulations standards, then the probability of that being the source of the problem is low. More likely it's a problem generated within the house. Condensation is caused when warm humid air cools down, which suggests that you need to improve ventilation in the room / house, remove or reduce the sources of humidity, improve the heating in the room, or all of these. As the problem is only in this room, maybe that's because it's not much used and therefore may has a shut door and maybe isn't heated often / much? At least I'd guess that the eves cupboards are the least heated / worst ventilated part of the room.

I believe the formula for the required airflow in m³/hr = Watts x 3600 seconds / ((maximum permitted °C - ambient °C) x density of air (kg/m³) x specific heat capacity of air (J/kg.°C) So taking 40°C as the maximum (a reasonable limit), and ambient as 22°C, then 1000W x 3600s / ((40°C - 22°C) x 1.225 kg/m³ x 1012 J/kg.°C) = 161m³/hr. Which is about 95CFM. So, to answer your question, yes if we ignore heat waves when the ambient temperature may go well above 22°C. There are no doubt other options, but the Shelly EM with a suitable clamp around the cable could be used to monitor the energy use. It also has an integrated 2A 230V relay that could be used to control a valve, though you / your electrician would need to study the manuals. Not yet used it myself, but I'm thinking of doing so to automatically switch on a kitchen hood if the hob or oven is switched on, though not sure when I'll get around to that. I wouldn't expect a problem with recirculating, as the MVHR remains in balance, but this is external extract. However it would be interesting to get the thoughts of someone who ignored the normal advice and installed a kitchen hood with external extract (though they probably wouldn't run it for as long as a movie).

It's because modern washing machines use much less water. If they draw what they need from a hot pipe, that's often not enough for the hot water to actually reach the machine - you're starting with cold anyway, while the hot water in the pipe goes cold.

Well that's clearly better than 2,000W. Maybe a motorised valve in the ductwork? I know that Atlantic make one in France - EAN 3416085437711 - so there must be similar available in the UK.

Long overdue, IMHO.

Not something I've tried to do domestically, but here are some thoughts. The initial one being that putting 2,000W into such a confined space may need an alternative solution, if it will really be that much. The AC fan you mention runs at up to 205 CFM - that's 350m³/hr, albeit half speed may be enough to keep the temperature down. But that is going to disturb the operation of a regular MVHR system. It may be OK if free of obstructions, but if you're sucking 200m³/hr past it anyway... As a rule of thumb, an unobstructed 10mm gap below a door is good for up to 40m³/hour. So you'd be looking at a fair sized gap. A dedicated air supply may be a better option - or perhaps fit a mini aircon unit instead of fans, which would work alongside the MVHR.

Apparently they're making a (small) comeback - https://www.building.co.uk/focus/the-return-of-the-clerk-of-works/5090855.article

Only from an office. It's a bit like wearing sun glasses - everything looks normal through the glass despite the tinting, until you see 'reality' through a non-tinted / open window. The biggest downside is that they cut the light transmission into the room significantly, which could make the room gloomy in winter. I wouldn't do it.

Building Regulations Approved Document A requires a minimum thickness of 90mm, so to go thinner than that you'd need Structural Engineer's calculations to prove that it's adequate.

Simply, plywood comes in Classes I (dry use), II (humid / occasionally wet) and III (unprotected externally / frequently wet). The old WBP would now be Class III - it's been that way for years, so someone must have cut and pasted a very old spec. Personally I'd choose 12mm Class I everywhere, since ventilation & tiling should stop the ply from becoming humid / wet in bathrooms, though you could upgrade to Class II.

There's also the option of adding a ceiling fan.

It may help, but at least some aren't suitable for use externally. Conbloc Paint Grade blocks aren't suitable for external leafs above DPC, for example.

Lignacite Fair Face, for one. https://lignacite.co.uk/products/lignacite/

Ignore! Height does play a small factor, but floor area is the biggest factor by far. Doesn't sound unreasonable for a utility room.

Illbruck FM330 also gets my vote.

1. If you use hard plastic wedges, it should be possible to work them out 3. A minimum of 3mm on normal backgrounds, according to BS 5385-1 5. Refer to the adhesive manufacturer's recommendations 6. Personally I'd only ever use a wet saw 10. Draw it out on the walls before starting, ideally with the help of a laser, to get everything arranged as you want it and to make sure that all the cuts are sensible - for example to avoid thin slivers of tile.

Choose a smaller tile? Big is certainly popular, but those are going to weight around 20 to 23kg per tile. That's not easy to handle or lay for the inexperienced / under-muscled.

Looks cool, but will be a (even more of) a pain to clean behind the bath with the screen in the way.

Agree with the above - go all-electric.

The best way of saving money in cut the heat loss, so the first thing to discuss would be what is and isn't possible when it comes to adding insulation, to ensure you'll be doing everything you reasonably can (and there is normally a lot that can be done). Then do similar for airtightness. With those strategies decided you can calculate the future heating requirement and invest in a heat source sized for that future need, which could well be a heat pump. You'll need to supplement with something else until the building reaches that stage (if you install it before then), for example maybe repurposing one of the existing boilers. In the immediate, I'd just spend a few hundred on replacing that annoying pump! You'll also need to consider how you deliver the heat, long-term. My preference is normally underfloor heating, but that's something that you would need planning into your refurbishment & boiler replacement schedule.

All fire doors in all buildings used to require automatic closers. That requirement was relaxed for private dwellings (except between the house and an integral garage, as your BCO requires), but in all other respects a fire door is a fire door. The change followed a report in 2003 identifying that closers were causing over 30,000 finger-trap injuries each year, and that many people disabled the closers or wedged the doors open.