Dan F

Do want real slate, but just not a heavies or anythingt too rustic. Those Tapco ridge/hip tiles might be a good alternartive to the concrete version though, if they can be used with slate..

Roofer has recommneded El Prado First (which is very similair to Del Carmen). Del Carmen Ultra is obvisiouly the best, but comes at a premium. You don't remember which slate you had the bad experience with do you? Yeah, I've seen the same. But in our case we are looking for something that not quite as thick and a bit smoother for more of a contempory look, and unclear what the best option for this is. I do have samples for Cupa 12 and few others due tommorow, so will see what these are like. I'll also give Burton a call, but given they only seem to sell Cupa slates, I'm not sure they'll want to give me a unbiased opinion about Cupa vs SSQ.

What do you use/recommend?

We are currently looking at slates, need to decide what we want to use in next couple of weeks. Looking at fairly smooth 5-6mm dark grey slates for a contemporary look (so not the heavies some people recommend) and have samples from SSQ and Cupa, and also been told about ESCO Merayo. Really hard to understand how they differ though, other than that the more expensive ones typically have a more consistent thickness. The SSQ Del Carmen slates definitely aren't cheap, so keen to understand @makie's experience.

Have you used them and had a bad experience or are you a roofer? Ideally you'd provide some context around this assertion..

Our PHPP "Heating load" comes out at about 3kW. Our traditional method "heat demand" came out at 6kW. We plan to use a 305L Mixergy tank (reheat time isn't quite so important) and we are looking at using a 7kW ASHP minimum. That said, we're being advised that using 10kW to give additional headroom wouldn't be a bad idea either..

That's not quite right; both the heating load and heating demand both take into account "internal heat gain" as well as "solar gain". The difference between the two is that the "heating demand" is in kWh and is per year (annual energy usage for heating) wheras the "heating load" is in W and is the energy input needed to keep the house at 20C on the typical coldest day of the year. You'll want to take a slightly more pessamisitic stance on heating load than PHPP though, PHPP tries to be realist which is good for modelling, but not ideal for specifying ASHP. Why? i) because the building might not perform as well as modelled in PHPP in practice ii) occupancy and other heat inputs might not meet PHPP assumptions iii) PHPP uses a design temperature that isn't particularly low (-1.5C in south east). iv) assumed solar gain might not be as much in reality due to shading, neighouring buildings etc. Agree on the other points, another thing to take into account is DHW cyclinder reheat time.

LoopCAD is another tool you can use to do heat loss calculations and then simulate UFH design. If you need UFH upstairs will depend on how well the house is insulated because even if UFH on the ground floor alone can meet heating demand, you won't want upstairs much colder than downstairs.

You could also request a quote from GBS (green building store).

Not mine either.. @Nickfromwales might be able to comment...

Not considered external blinds?

We have 310m2 and a caclulated boost rate of 370m3/h and will be using the Q600. My understanding is that the Q600 is good up to around a 460m3/h boost rate. If you need an even larger unit there is this model: https://www.bpcventilation.com/airflow-adroit-dv245 (930m3/hr!) (I personally would favour one unit over two..)

Any of those options should be possible shouldn't it? Isn't it just a sizing+plumbing exercise?

It's projected footprint of rooms within thermal envelope. This means an integral garage with no room above is excluded, but any first floor overhangs have to be included. The exact amount of PV you need is based on PER. If your PER is less than 45 kWh/(m²a) you don't actually need a full 60 kWh/m²AProjected*a. We are also targeting PH+ and these are our numbers: Heating Demand: 11kW Treated Floor Area: 305m2 Projected footprint: 208m2 PER: 30 kWh/(m²a) PV required: 38 kWh/m²AProjected*a.) = 7904kWh/yr In our case (south-east england) and ignoring shading (which is minimal anyway) this requires 27 x 360W panels split over east/south/west roofs. Regarding DNO and export, this really comes down to what you grid is like locally. For 10kW in our area we have the option to use single phase or three phase, but we've decided to go with a three-phase inverter because the bungalow we knocked down already had a three phase supply. You can apply for what you'd ideally want to do and then work backwards from there with most DNO's. Also some DNO's have a online map which will give you a rough idea. e.g. https://www.ssen.co.uk/generationavailability/

Yes. Yes. To get the most out of duct cooler you'd want a flow temp from ASHP of around 5C, but would need to ensure UFH temp is not much less than 17C to avoid condensation on floor. This can be achieved with correct design though. Yes. This is the same for UFH heating and DHW as each has different flow temperatures typically. Do you see this as an issue? ?

Pretty much the best you can do, without using staggered/double studs, which gets you -59dB Rw is: - 50mm rockwool - 2x12.5mm soundbloc on either side. - Resilient bars. You also need to think about structural and flanking sound transmission, it's not all about how much sound reduction you get through the wall itself.

Not simpler really as you'd have 2 x ASHP, but simpler plumbing yes. It's not just the distance but how much space you have for flow/return pipes. Moderate distance isn't a major issues if pipes are well enough insulated. Zehnder aren't the cheapest MVHR unit, but they do sell high capacity units which can easily do a large house. Airflow also have high-capacity units.

Exactly and you can use it for supplementary heating too if required.

No it doesn't, it's a warm loft. But you still really want to get the cooled area to the room.. There might also be a condensation aspect to it, but like you I would have assumed any condensation happens in the duct cooler itself primarily especially if all ducting is in the thermal envelope.

That is exactly the same situation as us. Our calculated cooling demand is 1.1W/m2 with blinds so that's only 335W so any cooling via MVHR for upstairs will be plenty. Do you have/plan an ASHP? If you do then you simply need a duct cooler (VEAB or ComfoPost). If I didn't already have an ASHP planned i'm not sure i'd consider those overpriced MVHR based approaches at all, and would instead look at aircon/fan coil. This might be down to the manufacturers that the suppllier you got quote from use. Not all MVHR manufacturers have large volume units, so they may prefer to seel you a 2 x vent-axia rather than go with a different brand.

The insulation, I thought, was primarily to ensure the cold air gets to the rooms and isn't lost in the roof space. Comfopost datasheet uses 7C in datasheet, but this would depend on cooling demand I think...

Yes. But there will be a single insulated duct from duct cooler to a first-floor manifold in roof-space. This means that the insulated 89mm duct runs are shorter, and as it's only the supply ducts so it's not a big deal, especially if you do it as part of first-fix.

We will be using a ComfoPost unit (https://www.zehnder.co.uk/comfopost-range) to cool MVHR supply air to upstairs room. @Bitpipe is spot on though the limitatins of using this approach. In our case, this is on top of i) external shading ii) UFH cooling so it really is just a solution that allows us to compliment ground floor UFH if/when needed on first floor, rather than our primary overheating strategy. Given we're still building, it's yet to be seen if we'll actually use this much though.. To use this approach you need to: - Have ASHP to supply cold water. - Insulate the ductwork that will be supplying cold air. - Be confident that it will supply enough cooling power for your needs, this will depened on solar gain, orientation, shading etc. (or use it alongside something else) The ComfoPost data sheets give you an idea of how much cooling power you can get from one of these units based on water temperature and ariflow rates. VEAB is another manufactuer of these units.

The commercial options I have seen use brine loop and heat exchangers, which avoids some of the concerns but adds to price. For our build I modelled the use of a gound brine loop in both winter and summer: - In the winter the benefit (given very high level of insulation and high MVHR efficincy) was very low. - The benefit in the summer was more significant, but given we were already planning PV/ASHP/UFH, we felt it made more sense to do UFH/MVHR cooling in the summer with free PV, rather than add another system and additional cost.

Same here.