Ommm

We have a loft conversion with a long strip of east-facing glazing. It gets very hot in the morning and the windows are small so it's slow to cool down afterwards. I've fitted 50% window film which helps, but the heat has still got in by then. The existing uPVC windows also have perished gaskets so the wind comes through. I've been thinking of installing roller shutters on the outside to block the heat. The problem is that the existing windows are outside-opening casement, which will foul the shutters. Inside-opening casement won't work either. Which leaves me looking into sliding windows (openings roughly 700mm high x 1800/3000mm). It seems there are few suppliers of these, mostly in aluminium. Anyone have any experience? There are some more suppliers of sliding doors - is there a good reason why you can't make a short door into a window? There are also suppliers of uPVC sash windows - I wonder if those could be used in a horizontal fashion?

Do you reckon the fan coil units would make sense over a separate air-to-air split unit? I've been looking at an ASHP for heating, but we have a loft conversion which gets hot for about 6 months of the year. Window gain and lack of thermal mass are issues (it's lightweight wood/plasterboard construction, and we can't really add masonry for structural reasons), but it just has a lot of external area and in summer the temperature can sit at 20+ all night so there's nowhere to drain the heat out to. Being lightweight should hopefully mean it's quick to flush out with active cooling, and then added insulation (my current WiP) should help keep it cool, and more should reduce energy requirements. The advantage of ASHP cooling is only a single external box, and not having a separate radiator and indoor A/C unit (space is a bit limited for both in the rooms). I'd be looking at the radiator style fan coil units. Plumbing into a separate ASHP zone would be feasible, and a condensate drain could be tapped through the loft into the existing soil stack (although I'd be worried about it freezing and backflow of sewer gases) or out of the soffit (backdrafts of cold air from outside?). The single-panel radiators will likely need replacement for an ASHP anyway. On the merit of the split unit, it's simple, ubiquitous in other countries, easy to fit, and the failure modes are well-known. I also can't work out how it plays with using the ASHP for hot water - supposing somebody has a shower and the tank needs refilling, does the ASHP cycle between pumping cold for the rooms and hot for the water? Does that kill performance? I suppose it's not a big problem when it's that hot - people might like a cold shower! If you have an ASHP sized for heating a whole house (say 5-10kW) then would it be feasible to cool say 30m2 (obviously that rather depends on heat flux, but as a rule of thumb)? But I'm also curious how well the air to water ASHP compares for cooling with an air to air A/C unit. Is the A/C unit more efficient?

Thanks, lots of food for thought. My questions were made up as I thought of them so definitely a bit stream-of-consciousness ? A few clarifications... I've been looking at the RHI and the Green Homes Grant. We're eligible (I think) for 10K of GHG, which must be spent before end March 2021. Needless to say, all the installers are going to be very busy over the next 6 months (the GHG is a bit of a poorly thought out scheme where there's no time to train up any more staff). The GHG is paid upfront but deducted from the RHI payments, meaning you get the same money as the RHI but don't have to wait for it. That means there's a perverse incentive to spend more on eligible items, since it'll mean once you've expended your GHG you get the remainder as RHI (but you have to wait for that part). The RHI has been extended to March 2022, so slightly less pressure on that front. The boiler looks like it'll run inefficiently but is still operating - unless something else happens. The tank is almost full (got some at 19p/litre and used little over the summer). The main urgency is the GHG deadline and contractors' busy order books. I agree with fabric first approach. although there's a limit in a place you're living in. Loft access is horrible (no parts of the lofts are more than a metre tall, really awkward hatches), so I'm pondering about doing that insulation myself to avoid builders traipsing around the place. It would need to be carefully designed due to the construction - plain old fibreglass would be problematic (due to height restrictions). I've been in touch with a local company but they look like basic fibreglass-stuffers, as it seems is the insulation under the Energy Company Obligation (who want to tick boxes as fast as possible). The windows aren't anything to write home about but I'm not sure replacement would be covered under the schemes, nor make a huge difference (eg double to triple - since the existing panels look in good order). Low-E film may help a bit. Floor insulation and UFH would have been something we could have done before moving in, but we already had our hands full with redecorating, and there was a pandemic on so even basic supplies were difficult to get. We didn't forsee the boiler replacement being that imminent and we can't really tear up the floors at this point. I'd really like to do the flat roof but there are few approved contractors who will cover flat roofs, and the need for scaffolding means I reckon a non-approved contractor will be about 3K... and it doesn't leak at this point so doesn't seem urgent (I'd actually like to use the opportunity of having scaffolding up to add PV too - but that would be too much right now). Good idea about getting a new EPC. Is there a way to find someone who isn't just doing the estate-agent tickbox thing, but will do a proper assessment? (I have a Flir thermal camera and have been taking pictures of things - gives me some ideas, although we haven't had cold enough days yet). Some of the ASHP vendors say the next step is an assessment for about £300, which they'll deduct if we choose to go ahead with them - but that would mean picking a supplier which we're not quite ready for yet. I suppose that's roughly what you might pay for a decent EPC. Maybe a plan might be to get the assessment and see what difference loft insulation is going to make, before going ahead and doing it. Then we can assess what impact it would have on the ASHP sizing. We probably want to do the insulation anyway for cost reasons, but would be good to find out what to do first.

We moved into our current house in the spring. It's a 1960s semi-detached 4 room bungalow in Cambridgeshire, brick construction and a tile roof. Sometime in 1970s the loft was converted to add two rooms in the roof. The property has an oil boiler, electric shower and a woodburning stove in the living room. Cooker is electric. EPC was done in 2011 and is E54 – and says the area is 99m2. There's cavity wall insulation and ~20 year old uPVC double glazing. The conversion has vertical stud walls and dormer windows facing east. I've been fitting window film to the dormer windows (the solar gain in the summer is massive). The loft floor has 100mm fibreglass insulation and 100mm fibreglass batts are behind the stud walls in the conversion. I'm guessing the ground floor is uninsulated beyond the wood flooring and carpet underlay (there's an air brick going under the floor but I don't know the floor construction). The site appears to be relatively windy, although that's hard to compare. It's unclear if the conversion flat roof is insulated - thermal camera pictures suggest it might not be. It's been on the todo list to look at replacing the boiler, and it has now been declared unserviceable (although still working inefficiently for now). We haven't been in for a winter so we don't know what the oil consumption is like. The boiler is a 11.7-14.7kW model which appears to have been fitted with a jet hotter than 14.7kW (hence its impending demise). The radiators are mostly single-walled on conventional copper pipes (~20mm diameter). In our previous place (a sprawling 3-bedroom bungalow, worse insulated but with solar thermal) we used 1200 litres of oil over the year, which is 12400kWh. We only ran the heating sporadically on '1 hour' mode for maybe 4-5 hours a day though. I've been looking at ASHP but I'm a bit uncertain as to how it would work in a retrofit like ours. The RHI and GHG and our current boiler demise make this a bit more pressing than it might have been. I'm assuming that an ASHP installation would also involve improving the loft insulation and plugging any air gaps (eg under the conversion floor). We wouldn't be able to install UFH so that would leave us with radiator upgrades I presume? We'd replace the hot water tank with a thermal store and fit a tank-fed shower. We might also look at solar thermal or solar PV (lean towards thermal because roof space is limited and it works out a bit better with RHI and GHG). We're also concerned about noise - we're going to view some ASHP installations next week to hear for ourselves. Some questions: Is this kind of property suitable for an ASHP, or is the insulation just not good enough? I've heard all the horror stories about undersized ASHPs in insufficiently insulated houses, but I don't know what's 'good enough'. My wife likes to have the place cool, and likes opening windows for the fresh air. If we set the temperature to say 18C, would the system cope with the occasional window open or would that kill the efficiency? It would only be in one room at a time (except during the summer when we wouldn't run the ASHP). I don't think the house would be suitable for MVHR. We also have cats so closing doors is more difficult. Given the 'upstairs', how do we prevent all the heat escaping into the upper rooms and downstairs being freezing? With a boiler there's a constant large heat flux into the room – I'm not sure you'd get that with low temperature rads. Obviously TRVs would reduce the output upstairs, but I'm concerned about hot air escaping upwards. Can radiator upgrades be done by replacing single-wall with double/triple wall, ie keeping the same radiator wall area? Some can be enlarged but those below windows cannot. Others are in awkward corners, eg kitchen with limited wall space. The woodburner is drawing in room air. Would that drive a coach and horses through our efficiency? Obviously when running it is going to emit heat, but when not running there may be some leakage (eg you leave the fire to die down overnight but it still needs air, and nobody will be there to close off the vent when it goes out). Is there any way to reduce chimney leakage (automatically?) Would it be too taxing to run the heating at a constant cold temperature say 17C and occasionally 'boost' up to say 20C? We might boost using the woodburner, but other times we might want the ASHP to do the boost. I have quite a bit of computing gear that emits heat (eg 400W server). This can cause overheating in the summer when there is solar gain from windows. I'm concerned that further loft insulation is likely to make this worse. Is there anything I could do to mitigate uneven heat input into the house? It would be neat if I could extract heat from these appliances into the thermal store somehow. In the summer cooling would be very much appreciated. Assuming we fit an ASHP that supports cooling, any pitfalls? I assume I'd need to install fan coils off a separate port of the ASHP, rather than the heating loop? How does this compare with using a simple split-unit air conditioner? Would it make sense to fit fan coils instead of rads, so they could do both heating and cooling? How would they compare size-wise? (My wife is also sensitive to noise so we might be looking at fan-off mode for heating, with the fan for cooling only). I'm also wondering about other options. We're off the gas grid. GSHP is going to be expensive (only 150m2 of garden). Biomass seems like a lot of hassle, and space is constrained for a boiler house. A neighbour has LPG which means the front garden is dominated by an ugly LPG tank. I would quite like to recover the space used by the oil tank so moving away from oil would be handy. Wonder whether some air-to-air split units might be easier than an A2W system (although they would probably fail the noise test). Or maybe a combination of smaller ASHP plus split units? I don't really want to get another oil boiler, but wondering how risky ASHP is...

Hello! After a couple of decades renting we finally managed to buy our own place, a 1960s semi bungalow in Cambridgeshire. I've had DIY tendencies since age 6 and now I get somewhere to use them properly. The current major project is heating replacement, and there are plenty more projects in the pipeline! Thanks in advance for all the advice!