Iceverge

I wager that if you were to connect something like this to both the extract and supply sides and leave it run on extract like MEV for a month the mould and damp would all disappear.

I like the simplicity of the idea but I fear the price of insulation would just go up. People don't seem very price sensitive to the cost of it anyway. Plenty of people use PIR and phonetic where a much cheaper but slightly thicker layer of EPS or mineral wool would do. Instead perhaps over 5 years ratchet a progressive VAT burden to higher users, much like income tax. It would become more financially attractive to use less and generate more for higher users. EG if you live in a small house even with a poor EPC you'll still use less than energy than someone in a new 400m2 mansion with a pool. The later would pay the same for their first kWh but much more for the extra they took.

Yes but..... Say in theory if you ran a COP of 3 (3 units of heat extracted from the waste, 1 energy put in to make up the losses) on your DHW heat pump you should be able to return the waste water to the mains at much the same temperature as the mains water in. However if you were to add space heating to that you could well end up freezing the out going sewerage with the heat pump. Bugger. Even if sewerage is cooled significantly it will start to have processing and flowing issues. If you want to waste less heat from water just put a water heat recovery on the bath and shower wastes. Alternatively shower in the bathtub with the plug in and leave the water there until it has cooled to room temperature. You could get 2/3 of your energy back as heat to the room this way. V cheap win.

Yup,cavity wall full fill usually with closed cell foam, new build or remedial. Walltite and Isothane are two brands. It's at least 4 times the price of EPS beads, can glue failed cavity walls together. Has been used to water proof walls in flood zones. If not done well can shrink and crack the walls. It has a mega GWP however so not a particularly environmentally good choice. On another note my uncle had his house done about 10years ago with open cell foam in the cavity which is not recommended AFAIK. Probably by one of these disappear into the mist type installers. However it's been quite successful. Much warmer house, less drafts and the condensation/mold is gone.

Yes and no. The actual theoretical U value will be fine. It's just the realistic as built one will leave you disappointed. PIR boards are notoriously difficult to fit well in cavity walls so it's almost impossible get the advertised performance. If you have any residual cavity I would consider getting it filled with closed cell foam. My neighbour did this and is happy with the result as it will provide a good level of airtightness and prevent thermal looping. I would keep away from PIR in the roof. Especially as it's a cold one. Mineral wool will be much cheaper and far easier to fit. Blown cellulose is a top choice if you can get it. It's what we used.

@Indy I've been plugging away at this for a couple of hours on sketchup. First here are the elevations continuing in the style as before. As before I have no idea if the neighbours will be overshadowed or overlooked badly with this design. The council may be dead set against it too. Obvious points to note are. 1. Same footprint as your existing design. 2. Simplified roof. Just a hip roof with a flat GRP rectangle in the centre. 3. Fake chimneys only. 4. Open porch/balcony added to the rear. BEFORE AFTER Now for the floor plans. BEFORE + AFTER The foot print is the same I;ve done my best to keep the positioning and sizes of the rooms as you had them. Changes to note: 1. I've added side windows to the porch. 2. The hallway is more defined and has built in storage. 3. The study has an additional south facing window, built in book shelves and a glazed door with sidelights to brighten the hallway. The Storage opposite is symetrical. 4. The generous sized WC (wheelchair accessible size) has a south facing window and the door into the hall has a fanlight to do the same. Symetrical with the door to the visitors suite opposite. 5. The Visitors suite enters into a large dressing area with a tall window. The bedroom has an extra window and some shelving. It is further removed from the hallway for privacy and noise. 6. The central hallway is the part of which I am most happy! The staircase is much more of an event, fitting of such a larger house. Storage underneath. The South facing tall window will give tremendous light. Above is a surrounding wrap around landing and in the flat roof 3no 1m2 velux flat roof lights. 7. I've removed the niche for the ASHP. it would be more effective in the front garden with a stylish screen. Where it is it's awkward to build around and might be continuously defrosting due to lack of airflow. Also I'm not too enamoured with such a high current device enclosed on all but one side by the house re fire. Domestic bliss calling here............................................ I'll finish when I get a chance!

Realistically I think it's cheaper. 8% in time and money isn't long disappearing into an old building with all the sins of the past that are lightly to be unearthed!

The reality is that unless you've got the space in front of the house almost entirely boxed in the the air temperature on anything other than a completely still day will be almost exactly the same as ambient. If you do have a sheltered corner the ASHP will certainly immediately stir up and mix the air with the ambient. If you were building a gigafactory and one side was in a shaded valley and the other side to the south of a large hill then maybe it might make a difference. A house is simply too small and the heat pump needs too much air for it to work. I think the confusion and intuition is to do with how we feel sitting to the north or south of our house. The sun's direct radiation, and the lack of cooling breezes make all the difference rather than the air temp. Radiation would help an ASHP a tiny bit, and I mean tiny compared to the effect of all the air it's processing. The difference would be much less than 1% I wager. Other factors such as the fan struggling to draw too much air because the ASHP is too enclosed and a poorly insulated water pipe will have orders of magnitude more significance.

Don't know. House too airtight. (0.31 ACH50) No air can go out if it can't come in anywhere.

There's just far too much air being moved. Quick sums say a well built house of about 4kw continuous heating load will need about 32 tons or about 40000m3 of air per day for its ASHP (~ 16 Olympic swimming pools if you work in TV units). Normally the air on both sides of a wall you mentioned will be almost exactly the same temperature. It's the direct radiation from the sun makes your skin warmer. Even if there was a very localised warm pocket of air it's lightly to be in the tens of m3 and would be displaced in under a minute and replaced with the ambient environmental air. Defrosting I gather is a function of taking the ambient air below it's dew point rather than the actual temperature of the air alone. This can be avoided by having a correctly sized heat pump, more specifically a correctly sized heat pump evaporator fan unit to ensure enough passes thought that none of it is cooled below the freezing point of water vapour. If you're regularly defrosting your heat pump is overloaded and the battle is largely lost at that stage. There is a trade off to be done with accepting a very small amount of this in the worst conditions VS the cost of upgrading to a larger heat pump. The increased COP in higher ambient temperatures comes from lower fan energy demand due to reduced need for airflow( to avoid vapour freezing) and a greater delta T in the heat exchanger reducing the pumping requirement for coolant. ( one of the reasons inverter pumps are better as they can match the pumping speeds ( air+water) to whats needed only). All this is top of my head schoolboy physics so I'm happy to be corrected if anyone disagrees. TLDR. Heat pump in the sun makes no difference. Avoid defrosting by buying a big enough ASHP.

The terminology can be tricky here. Extract and exhaust are opposite sides of the heat exchanger. Your supply will always lag the room temperature a bit (in heating climates) as the heat exchanger is less than 100% efficient. Beware the internal heat exchanger temp probe may not be too accurate either. Perhaps verify with an external thermometer.

I think you should price up a bulldozer renovation. You might be surprised at how little difference there is vs a complete remodel for a vastly superior end product.

I suspect that'd probably be similar to the south of Ireland. What is the optimum fan direction then, blowing the same way as the prevailing wind?

Hi Russell, Can you elaborate on this please. What grade of EPS and staples did you use? I'd prefer to avoid PIR if I can for future projects.

I think this merits further study. Pull out some real data. Have you any simple thermometer to keep an eye on temps for us @joe90 I get the feeling it might be a very useful element of low energy building. All the benefits of massive glazing without the heat loss or overheating. "The selective use of solar gain through manually operated glazed appendages on domestic housing" Or a conservatory m8. ?

Yes didn't think about this. One could probably do an analysis of wind direction Vs heating load to get an optimum direction to point the fan. Then put the ASHP on the apex of their roof to maximize wind flow

I really like the design. One of the more thought out examples I’ve seen on here. certainly better than our house. However one aspect of your brief keeps bugging me. The need for natural light. Typically light from the South can penetrate about 4m into a room. Diffuse light from the North a maximum of 3m. Looking at this I can’t help but feel your kitchen will be very dark towards the centre of the house, the upstairs landing similar. The master bath and B4 will take the lions share of the sun upstairs while the study may suffer from overheating and the library/sitting to the south west will be (perhaps) rarely used during daylight hours. I would consider a rejig or the rooms. I would bring the kitchen/diner to occupy the East side of the ground floor( ideal for morning) stretching from South to North and the lounge to central rear for views of the garden. The projecting extension could be moved to the east side to accommodate both the inside space and with a roof terrace omitting the need for a separate balcony. To bring more light to the centre of the house I would make the staircase more spacious leading right to the top floor (may have fire safety considerations) with a pair of large remotely operated Velux’s on the top centre of the North roof. These would have a “Halo”effect on the hall being really visually striking as you entered the front door. If done well it could look like a stairway to heaven! Additionally it would be very effective as stack ventilation during cooling months. The master ensuite is terrifically large but if you were to make it a bit smaller it would still feel very spacious thanks to that terrific bay window. Take that bit and widen the dressing room slightly. Put a tall window in the east wall ( frosted perhaps for privacy) and a large mirror on the West Wall. Then line the North and South walls with cloths storage. (corner cupboards/storage are too difficult to use well. Finally glaze the bathroom door (mayby something funky like frosted stained glass). This combined effort would take the dressing room from a small dark room full of messy corners into a bright enjoyable area to get clothed. Now for the part I’m certain I’ll get more detractors on. I would drop B2+ensuite down a floor in the same position and raise the utility and study up a floor in their place. ( maybe put the study in B2 and leave b3 as is) Practically unless you’re a die hard “hang the clothes on the line” type there’s far less benefit having a utility/laundry near the garden rather than near the bedrooms where all the cloths live anyway. Realistically I cant see the downstairs utility door being used all that much either. A good door is three times the price of a good window. An upstairs north facing study is isolated from street noise, has even diffused sunlight (much better than direct for working in + video calls etc) and importantly, for those of us who have seen covid test our belt buckles, far away from the biscuit box! A downstairs bedroom with access to a shower is practically so so useful. For having small kids its brilliant to be able to change dirty nappies and wash them up on the ground floor. ( Even with years of farming and various types of manual labour, nothing has been as testing on my back as children). Its great for friends and relations who are not as well able to handle stairs to come and stay. Also being on a different floor it gives good privacy to guests, au pairs and inmates alike! Finally, although we all hope to be active for many years its quite likely a temporary injury will come sooner than you expect. I fell off my road bike and bashed my knee a few years back and although it was only a week, having a choice of living upstairs with a bathroom or downstairs with the tv and kitchen was not as dignified as it could have been. Then there’s the old age debate which of course is well known. I know you have provisioned for a lift. This isn’t a terribly robust path in my opinion. The likelihood is that if you aren’t building it in on day 1 you won’t do it until you really have to have it. Then you are assuming that you’ll be in a position to splash £20k minimum + inflation and be able to wait for it to be installed. Remember older people can find it difficult to access credit and some illness and accidents (as i found out myself) can come very suddenly. Overall though I love the feel of the plans, the room shapes and scale. I have a couple of thoughts on the outside but make sure you’re really certain if the layout first. Good luck!!

We have a hole through the wall with a 150mm duct and a magnetic backdraft flap. Have to put a window on tilt when the extract fan is on 2 or 3 due to good airtightness. It works fine. I wouldn’t be afraid of a recirculating extractor with a good carbon filter mind you.

ASHP simply move too much air to make much use of relatively small localised warm air pockets. A 10kw heat pump moves up to 3000m3/hr. Say you were to allow an hour for each airchange to gain meaningful heat in a nice suntrap that was sheltered up to 10m high with 300m2 ground area .Then put the heat pump in the middle. On a still day it would make a measurable difference to the performance of your ASHP. However you’d be better off just putting the entire house in the said suntrap instead! I wager a better ASHP location would be as close to the house as possible to reduce pipe heat losses and in a naturally windy area so the fans don’t need to work so hard.

Is the house built yet?..........

It might sound like a silly question but were the filters OK? I know our first set only lasted a month or so after we moved in. A blocked set might have confused the MVHR unit. In the meantime maybe get 2 inline fans and extract from all the house ( supply and extract) and leave windows on the latch for trickle ventilation. It should suck all the moisture our of the ducts and kill the mould as well as giving you some needed ventilation. My suggestion for cleaning the ducting use a vacuum to draw a string through the ducting to/from the manifold. Then tie a rag firmly on one side and pull it back to clean the ducting. Start with a smaller rag and work up until you have something that cleans well but does not get stuck.

Did a floor with a mate last week. Used glue and 28 screws per 2440*1220 sheet. The reason that number was chosen was that was the amount of screws we had! Seems fine. A nail gun would have been much faster however.

Before you submit please have a sence check on the glazing to the west and east. It will make the house almost unusable if you continue as is. I've been thinking about how to bring in more light. I would raise the eves height and go for a flat GRP section in the middle of the roof. This would allow you to include some skylights in the centre of the master bedroom ( vaulted ceiling for some real wow!) Also I would dispence with the balcony and push the master bedroom towards the garden. Widen the hallway and have a large skylight over in the style of an atrium. It could look amazing and would transfer the feel of the centre of the house.

Excellent effort. Only one thing I'd change. You will loose a lot of heat via the route of the yellow line. We took the EPS beads well below the DPC and dispensed with the cavity tray. Have a look at the below post about this. The second 2 diagrams tell a lot. Steel beams far from the perimeter of your slab might not benefit much from a thermal break as the path to loose heat to the outside will be so long. @OldSpot had some good insights RE insulation DPMS and UFH clips here. It might be worth considering.

Good good. Maybe get a £5 humidistat to get some before and after RH readings. I installed a central. MEV in my parents loft in their uninsulated house. It has reduced the damp in the house for sure. Any chance you’d share some of the thermal pics. I’m interested in purchasing one,