Crofter

So This should all be a solvable problem. But I'm realising it's fairly involved. I've not heard great things about the system design for A2A by the 'experts' and I'd like to get my head around the principles. So I guess I need to do a rough heat loss analysis first, to size the unit. For example, using Heatgeek's rules of thumb I'm getting maybe 60w/M2, which for my 93m2 property is about 5.5kw. That's about half what I was expecting. What happens if I oversize a good bit, up to say 10kw? Will the system cycle too much and lose efficiency? Next, pick a suitable ASHP unit and start playing around with flow rates and temperatures. That should let me start getting a handle on duct and vent sizes, and layouts. I'm finding very little info on all of this online. I suppose some of the principles will be the same as MVHR, but I guess it's a much larger volume of air being moved, and I'm going to want different rooms to be at different temperatures.

This was my experience too) Highland Council thing, perhaps?) I could just squeak in to the requirement, but it relied upon vegetation being cut back on the verges for 90m either side of my access. This wasn't my land so the need to 'demonstrate control' couldn't be met. But they accepted it. My backup plan would have been to point out that it was their responsibility to trim back the verges. A couple of houses built after mine, on the same road, had nothing like as good visibility, and still got through. One other thing that came up for me was that my LA have two different access standards- one is for a single house, the other for a mini estate of up to four houses. The junior planning officer who first dealt with my application initially demanded that I use the larger access, which physically wouldn't fit on the plot, because it would be shared between the house and the field behind it. Despite the field having alternative access, and fields not needing the same standard of access as a house. Fortunately he was over ruled by his boss who saw sense.

That low level wall outlet is basically what I'm hoping to do. But fitting a 200mm duct in to a 100mm stud wall will be interesting. I guess I can split it in to four 100mm ducts...

Lifting part of the floor isn't a great option, it's continuous pine T&G boards with the internal partitions built over the top. I think it would be pretty destructive and the floor would never be the same again.I've also just laid laminate through about half the house and don't want to lift that again! I really don't mind working underneath- there's about 2-3ft clearance everywhere. I replumbed the entire house recently and shifted everything from the loft to underfloor. The ducting in looking at is the same idea as I used for MVHR in my other house- flexible, expandable, lightweight, so dead easy to work with. Will need support but nothing complicated. I see in the US people use floor gratings. It must work, otherwise they wouldn't be doing it. But it feels a bit wrong to me, for some reason. Can imagine it working in rooms with hard flooring, I suppose, but not so much with carpet. I think I may have to resign myself to building a box-out and just have it positioned where it's partially hidden, e.g. behind a shelving unit.

Exactly. I don't want to force air down from up near the ceiling, I want it to emerge at floor level where it's needed. I expect a ducted system will be quieter than a mini split. I'd also like to be able to duct warm air to every space, which gets expensive with splits. But ducting is cheap. I don't really mind working under the floor. My loft is so full of junk that it's probably easier to work down there. Condensation drain is easier. Connection to outside unit is easier. Everything seems to point to a floor level installation, when the primary aim is heating.

Standard appears to be 200mm diameter ducting. So not Bruce sized but not small either. Maybe this is why ceiling mount is much more common.

No MVHR, this is for my 70s bungalow, not the cottage. I'm pretty tempted to fit a conventional (non ducted) A2A in the cottage, but probably after I've fitted PV.

Ah but that's the Costa del Moray, where they have this strage glowing orb in the sky.

The floorboards aren't anything like as gappy as the air bricks!! Seriously, somebody else must have thought of how to do this. Scratching my head a bit, I can hide box-outs for the bedrooms and bathroom, thanks the built in cupboards. In the kitchen, vents could go in the plinth under the units. The living room is trickier, no easy answer there... What generally accepted as the best place to draw air in to the system?

I'm leaning towards an underfloor ducted A2A system. The systems I'm looking at all seem to be designed for ceiling mount, which makes sense in air con mode. And it's dead easy to stick a vent in the ceiling. But for heating, it makes sense to pump out heat as low as possible. Being in the north of Scotland I don't expect to need cooling often, if ever. What's the standard practise for low level vents? I don't really want a grating on the floor itself. I'm hoping that it might be possible to fit something within the depth of the partition walls, but that's only 100mm and getting up through the wall plate will be a PITA. The alternative would involve some sort of box-out affair, which doesn't seem very elegant. I don't want to reinvent the wheel here...

I expect it's to do with a presumption against air conditioning. Planning is just as much about how a property is used and affects the surroundings, as it is about aesthetics.

I did not know that! In terms of aesthetics, there's not much difference in the external unit for A2A and A2W, is there? Both just a big white flat box with a fan in it.

Fair point about whether f-gas is needed on most installations. I'm probably being swayed by my own plans to install A2A. The more I've researched it, the more I like it. Seems a bit crazy that it's not more popular.

Sounds interesting! Did you go straight in to a classroom and start the courses, or did you get your hands dirty first?

Can't find it now but it would have been on the first page of a Google search. Courses cost around £900+VAT, 5d duration, and they recommend that you are working towards SVQ level 2 in refrigeration/AC engineering- which means you need to working in the industry already. However they also say that you can sign up without these qualifications, if you can persuade them that you have relevant experience. Could be a bit of a chicken and egg situation...

My crystal ball suggests that there will be a lot of f-gas cert engineers needed in the near future. I'm toying with a career change but I'd be starting from scratch (I don't have any trade under my belt). Is this a silly idea? I'm in my early 40s. I've found places offering the course and they're a bit ambiguous about entry qualifications- it sounds like you could blag it if you had some relevant experience.

No issue that I'm aware of, I've just more often heard about ducted units going on the loft space.

That makes sense. But most of the units I've seen on the market area designed for high level mounting. Any suggestions for a ducted system which could live under the floor. Is that a good idea? Would make condensate drainage nice and simple.

I don't think there's any reason not to, other than the extra cost.

I think the idea is that you have a gravel hardstanding and sit the Puraflo on that. But you'd really have to start talking to SEPA.

For external cladding? 🤔

I would have a good look around your local suppliers. The only roofing battens I was able to buy were either stained green from pressure treatment, or died blue. The latter were shocking quality, left dye running everywhere and split the moment a screw went near them. My own cladding is larch from a local sawmill. Half the price of a builders' merchant.

Lots of the ideas in this thread revolve around sight lines. For good reason. Lining up sight lines doesn't necessarily cost anything but can really change the feel of a place. It's one of the things that makes a bespoke design different to an off the shelf one. My own build was done to a tight budget (about £20k for 50m², plus groundworks/services). Here's some of the decisions I made to keep the budget in check whilst retaining what I think is a pretty nice finish: -My favourite tip is to avoid small windows. Consolidate all your glazing in to a few huge windows. Non opening if possible. You will get a much lower cost/m² with much better thermal properties. It's an absolute win-win. I was really surprised by how cheap a huge non opening 3G window was. -I'm also a big fan of bamboo flooring. I'm not up to date with prices but about five years ago it was half the price of decent oak, and much sturdier. -you don't need solid oak skirtings and door linings. I went with MDF which was a fraction of the cost and also much easier to fit. Need to screw the skirting to the wall, or messed up amitre? Just fill and paint afterwards. - larch and corrugated steel make very cost effective finishing materials, quick and easy to work with. - it's not necessary to spend big money on kitchens and bathrooms. I've seen people spend more on a kitchen tap than my whole bathroom cost. I went secondhand for all my kitchen appliances, but bought good brand names (Bosch and Siemens). They've outlasted the cheap brand new stuff I bought in my other house.

It wasn't a cost decision, although the 50mm solvent weld that I used is really cheap too. The decision behind it was that I could run the SVP up the outside wall within the depth of the battens for the timber cladding. Means it's completely hidden from view yet external to the house in case of any leaks, and no AAV needed.

It wasn't particularly cheap. Back in about 2016 I paid around £7k by the time the septic tank and Puraflo was installed. The company would not do a supply-only deal so it was about the only part of the entire build which had to be handed over to someone else.