Crofter

In the absence of a proper heat loss calculation, I've been looking at a few online tools. A radiator sizing tool gives me 8.9kw Heatgeek's 'rule of thumb' suggests anywhere between 4.4-7.2kw. We are in a pretty exposed location in NW Scotland. Starting to lean towards the 10kw to give a bit of extra margin. But I'm also aware that with ASHP bigger isn't always better...

Any takers? Basically my choices area down to a unit which will modulate between 1.1-7.3kw, or one that does 2.1-10.4. There's a third option which can do 2.1-8.1 and has done nice air purifying features, and it's a tiny bit cheaper. I've heard that the ability to modulate down to a very low level is quite important for efficient running.

Took a while to dig it out but we seem to be averaging about 840kwh per month in the heating/DHW meter. Unfortunately this is partly based on estimated readings, and the occupancy is the house might not be representative of future use- it was used as a holiday let for the last three years, so people had little incentive to save energy, but also it was mostly empty through the coldest months (although there was nobody around to turn the heating down).

I'm not sure why that should matter. The site can be an address, where else is your builder going to send his bills 🤷‍♂️. It's very common to live on site in a static, not only are you saving rent, you're also saving commuting time. And it's dead easy to do on site meetings with people (trades, suppliers, building control etc) if you live there 🙂

Existing, but I can't separate out the heating and hot water usage, both are direct electric.

There is, but it would be a loft conversion, and I'd likely be installing a second system to handle that, probably with a couple of wall mounted units.

Fitting an underfloor ducted air to air heat pump. Installer has offered the choice of 7kw or 10kw. The 7kw can go down to 1.1kw minimum, whereas the larger unit can only drop to 2.1kw. I'm tempted to go for the smaller one, my understanding is that the lowest output is quite important as when this is too high, the system will start to cycle and efficiency will suffer. The smaller unit is also significantly quieter, and a little cheaper too. I know it's an almost impossible question to answer without a proper heat loss calculation. I've had a stab at it and generally 7kw seems like plenty, although the real figure will depend on how much heat we're going to lose through air leakage, which appears almost impossible to determine. So, what wins out, higher output vs lower modulation?

Time for a thread bump! How's everybody getting on with their Fakita tools? I'm in the market for a new drill for light work. And also, ideally, a car (12v) charger. Any links etc appreciated 🙂

After three years stuck in a somewhat damp shed, I pulled out my trusty old Makita chop/mitre saw and it... died. It tried to spin up feebly, then the blade brake didn't engage and it slowly span until it stopped. Fuse is good, outlet is good. I'm wondering if it's something simple like the springs for the brushes are stuck. Don't want to put a lot of time in to it if it's going to be a big job though. Any suggestions for what to check?

I think we're actually in agreement. It's both the design (shape, features) and build method that contribute to cost. Your point about doors is a good example. Another one would be ceiling height, or anything else where going beyond standard dimensions could lead to a lot of waste.

I'm not sure about that. It's easy to add things like dormers, integrated garage, complex shapes etc which all drive up the cost significantly. Stick to a simple box with a favourite volume to surface area ratio.

A small number of large windows, ideally non opening. Secondhand kitchen appliances (my Bosch oven was £50 and looked unused) eBay taps and shower screen Painted MDF arcs/skirts- very DIY friendly so saves labour as well as up front cost. Bamboo instead of oak flooring. You could be bold and not fit a heating system, it worked for us but the house is very small and very well insulated and airtight.

I'm struggling to find a supplier for a 1500mm tall window who will offer a top hung option. Any suggestions?

It's basically not worth the hassle. Lots of thermal bridges and gaps where your cables have to run so you wouldn't really get a full 25mm insulation layer.

If you can put your battens closer together that will help a lot. I had 600mm centres and there was no way 25mm counter battens would have worked, they would have bounced too much to drive the nails in. But halving that span should work pretty well I think. If you're including a cement board layer anyway, could you go frame-membrane-void and then use cement board cladding? It would give a more fire proof and lower maintenance alternative to larch.