Heating/Cooling - best combo to go for?

[G and J]

15 minutes ago, JohnMo said:

I did our differently to anyone else, I have seen.  I did the floor insulation, UFH and then 100mm fibre reinforced concrete, prior to any walls going up. Way easier, then the cost is concrete m3 prices, we needed a 36m concrete pump lorry also, and 2.5 lorries worth of concrete.

Did that make it cheaper then? (He asked, aware of how much he doesn’t know….)

[Iceverge]

On 23/11/2024 at 17:23, Indy said:

Thanks for the detailed reply. Just to make sure I understand, I'm going to break it down step by step - and please correct me if I've got this wrong.

 

1. Standard MVHR - no cooling added

2. ASHP with cooling function - may or may not be eligible for grant but if we have only 1 unit, then we can put this outside without going back to planning and do it under PD rules. 

3. Heat pump cylinder - 300 to 400l for 3 bathrooms and 1 cloak room. 

4. Wet UFH heating on the ground floor

5. Can I also put fan coils in certain rooms on the ground floor with the wet UFH? This will make them work as air con units in the summer when we run the ASHP in reverse. 

6. Any modifications needed to the ASHP to make sure running in reverse doesn't cause issues?

7. Wet UFH only in bathrooms upstairs, and not bedrooms? Will the fan coils work enough on their own to provide heating up to say 22-23C to keep the rooms at that temp? And what temp can they cool down to in the summer?

8. I currently have towel rads that run off the ASHP and then an immersion element that can be turned off or on. I assume this is the equivalent of electric towel rads?

9. Stupid question: the fan coil units will have plumbing connections to them I assume - i.e. a pipe coming in and a pipe going out?

10. Why not have thermostats in the rooms? Or can we replace the thermostat with the fan coil unit which I assume will have some sort of manual control on it rather than running of a central system?

 

With regards to floor insulation - we did speak to the architect about adding more but his opinion is that BR regs are pretty good these days, and coming from my baseline of a 1930s semi with no cavity walls at all - it's going to be a massive step up. This is what I have so far

 

Floor construction: U Value = 0.14 W/m².K

• 65mm. sand: cement screed
• 500g. Polythene separation layer
• 120mm. Celotex XR4000 insulation
• Polythene DPM
• Concrete beam & block floor to manufacturer's design

Wall construction: U Value = 0.15 W/m².K

• Render
• 100mm. Thermalite Hi Strength 7 blockwork
• 50mm. clear cavity
• 100mm. Celotex CW4000 insulation
• 100mm. Thermalite Hi Strength 7 blockwork
• 12.5mm. plasterboard on dabs dry lining, plus skim

Pitched roof construction (insulation at rafter level): U Value = 0.11 W/m².K

• Roof tiles
• 25x46mm. treated tiling battens
• 25x46mm. treated counterbattens
• LR Breathable roofing membrane
• 150mm. rafters fully filled with 150mm. Celotex XR4000 insulation
• 25x47mm. battened services void beneath rafters
• Celotex PL4060 (60+12.5) insulated plasterboard plus skim
• Proprietary felt support tray

Pitched roof construction (insulation at ceiling level): U Value = 0.11 W/m².K

• Roof tiles
• 25x46mm. treated tiling battens
• 25x46mm. treated counterbattens
• LR Breathable roofing membrane
• 150mm. rafters
• Unventilated loft space
• 19mm. plywood decking or flooring plywood for loft storage
• 75mm. Celotex GA4000 insulation above ceiling joists
• 150mm. ceiling joists fully filled with 150mm. Celotex XR4000 insulation
• Visqueen High Performance vapour barrier
• 12.5mm. plasterboard plus skim

COLD Flat roof construction: U Value = 0.11 W/m².K

• GRP weather surface
• 18mm. plywood deck
• Firrings to give 1:40 fall
• 195mm. joists with 150mm. Celotex XR4000 between joists
• 90mm. Celotex GA4000 insulation below joists
• 12.5mm. plasterboad plus skim

 

 

Is this built? 

 

 

Someone has been wined and dined by the celotex salesman🥴

[Indy]

5 minutes ago, Iceverge said:

 

 

Is this built? 

 

 

Someone has been wined and dined by the Celotex salesman🥴

 

Nope - just a spec for now. Build starts in Feb next year. 

[JohnMo]

8 minutes ago, G and J said:

Did that make it cheaper then? (He asked, aware of how much he doesn’t know….)

Not really sure, but for it made things easier for me, I did the insulation and UFH and the ground workers did the floor, and had no corners to mess with. It was also easy to get hold of. We were building the walls this time of year, without bringing it all to doorway level, I would have been waring waders. One disadvantage of lots of insulation in a floor - it gets wet then it freezes overnight, and stays frozen for ages.

[Iceverge]

4 minutes ago, Indy said:

 

Nope - just a spec for now. Build starts in Feb next year. 

 

Is there time to change much of the fabric spec. This will perform worse in reality than on paper. 

[Indy]

29 minutes ago, Iceverge said:

 

Is there time to change much of the fabric spec. This will perform worse in reality than on paper. 

 

What would you suggest? In the process of finalising the BR drawings which will include construction notes. 

 

It's not set in stone as such but I don't want to start changing things massively unless there's a noticeable difference. 

[G and J]

1 hour ago, JohnMo said:

Not really sure, but for it made things easier for me, I did the insulation and UFH and the ground workers did the floor, and had no corners to mess with. It was also easy to get hold of. We were building the walls this time of year, without bringing it all to doorway level, I would have been waring waders. One disadvantage of lots of insulation in a floor - it gets wet then it freezes overnight, and stays frozen for ages.

As we are thinking of using an insulated beam and block floor that’s a really interesting notion.  

 

So instead of a screeding team (is that what does screeds?) it’s a concrete lorry and a rake….
 

So the rest of the build happened off of the finished floor level….

[Iceverge]

10 hours ago, Indy said:

 

What would you suggest? In the process of finalising the BR drawings which will include construction notes. 

 

It's not set in stone as such but I don't want to start changing things massively unless there's a noticeable difference. 

 

Sorry for not picking this up earlier. The thread got a bit hijacked and I must have skipped it. 

 

 

Ok. I'll do my best, you'll have to widen the wall slightly but it'll save you thousand's and perform much better. 

 

1. Standard MVHR.

2. Monoblock ASHP to UFH ground floor only. Cooling if possible. 

3. UVC as you say is ok. Bigger is better. 

4. UFH on ground floor is good. 

5. I don't like fan coils. Unnecessary complexity in my opinion. Provide space  for A2A is easier in my opinion.

6. Don't know. 

7. No wet UFH upstairs just UFH electric under tiles. On ground floor bathrooms too. 

8. Include an electric spur for towel rads if you want them . ASHP runs too cold to do much with them.

9. Don't know. 

10. No thermostats in individual rooms.

Build well and the house will all be similar temp.

 

Architect is talking nonsense and spitting out Celotex's imaginary U values from their sales book.

 

 

Floor 0.13W/m²K

 

65mm screed. 

Separation layer. 

200mm of PIR or 300mm of EPS insulation 

DPM

Block beam. 

 

Walls. 0.18w/m²K

 

Sand cement Render.

Dense concrete blocks. (13N preferably)

200mm cavity full fill with EPS beads or mineral wool batts. Stainless steel wall ties. 

Dense concrete blocks. 

Wet plaster

Skim

 

Pitched roof. U value 0.12

Roof tiles. 

 

38*50mm tile batten.

 

25*50 batten up the rafters. 

 

Glidevale vp300/400 membrane taped at all joints and sealed to outer wall woth render over expanded mesh over membrane. 

 

11mm OSB sheathing

220mm rafters full fill with blown cellulose insulation or mineral wool.

Airtighess membrane 

50mm or 75mm or 100mm battened service cavity insulated with mineral wool.

 

2 x 12.5mm plasterboard and skim. 

 

Pitched roof with insulation at ceiling level. U value 0.12 

 

Roof tiles. 

25*38mm tile batten.

25*50 batten up the rafters. 

Glidevale vp300/400 membrane taped at all joints and sealed to outer wall render with render over expanded mesh over membrane. 

11mm OSB sheathing. 

150mm rafters. 

Invented loft space. 

22mm Caberdeck or OSB flooring. 

450mm blown cellulose or mineral wool insulation. 

Airtighess membrane. 

22*70mm service cavity 

2*12.5mm plasterboard and skim.

 

Flat roof Construction U value 0.11.

 

GRP

18mm OSB deck. 

38*50 batten across the rafters. 

25mm x 50mm battens up the rafters. To create 63mm ventilated space.

Breather membrane 

11mm OSB sheathing. 

220mm full fill rafters installed with 1:40 fall with cellulose/mineral wool. 

Airtight membrane. 

100mm service cavity full fill with cellulose/mineral wool.

2 x 12.5mm plasterboard. 

 

 

 

 

 

 

 

 

 

 

[Iceverge]

The design appears to have bifold doors and a chimney still. 

 

My advice is to change these to a pair of french doors with fixed side lights and to get rid of the fireplace. 

 

You'll save thousands of pounds and the house will be far less drafty. 

 

 

[Iceverge]

Another option is to include UFH on the first floor.for cooling mainly . What is it constructed from timber or concrete? 

 

 

As an aside do you have more drawings. The suggested roof methods may not be the best. 

[G and J]

49 minutes ago, Iceverge said:

The thread got a bit hijacked

You are a very bad person @JohnMo!

 

(Sorry!)

[JohnMo]

On 26/11/2024 at 17:04, Indy said:

Just looking at your drawings you have a lot of thermal bridging going on. Internal wall going straight to strip foundation. I would add a strip of thermolite (or similar) blocks to straddle the insulation. Same on the internal skin of outside walls. The first block of the internal skin do that in thermolite.

[Iceverge]

9 minutes ago, JohnMo said:

Just looking at your drawings you have a lot of thermal bridging going on. Internal wall going straight to strip foundation. I would add a strip of thermolite (or similar) blocks to straddle the insulation. Same on the internal skin of outside walls. The first block of the internal skin do that in thermolite.

 

Agreed. Whoever drew these up would be using basic details from 20 years ago. 

 

 

[Iceverge]

On 27/11/2024 at 08:24, G and J said:

UFH/house temp performance he expressed the opinion that it wouldn't help.  He has a 65mm screed and that's fine - "you won't notice any difference".

 

He's right. 

 

The meaningless phrase "thermal mass" isn't hated by people just out of pedantry. 

 

It's a term used to con those who don't understand physics out of their hard earned money. It really is a hateful expression that has resulted in too many honest people being conned. It's snake oil of the highest order. 

 

Phrases like "heat capacity" "thermal battery" and "energy store" "decrement delay" all actually mean something and can have quantifiable numbers attached to them. 

 

 

 

 

 

[Kelvin]

5 minutes ago, Iceverge said:

 

Agreed. Whoever drew these up would be using basic details from 20 years ago. 

 

 

Unfortunately common. Our construction drawings had standard concrete blocks which I swapped out. There was a very large house built near us that was on one of my training runs. The owner was there one day so I cheekily asked him for a nosey around as we hadn’t started building so had a curiosity. They had strip foundation walls running everywhere criss crossing the building for internal walls and standard blocks on the perimeter wall. 

[Iceverge]

Just now, Kelvin said:

Unfortunately common. Our construction drawings had standard concrete blocks which I swapped out. There was a very large house built near us that was on one of my training runs. The owner was there one day so I cheekily asked him for a nosey around as we hadn’t started building so had a curiosity. They had strip foundation walls running everywhere criss crossing the building for internal walls and standard blocks on the perimeter wall. 

 

The internal walls aren't too critical if you model them.

 

Of course it's no excuse and frankly accepting any easily preventable heat loss is negligent in my view.  

[Iceverge]

On 22/11/2024 at 15:19, JohnMo said:

am not impressed with UFH in bedrooms, would do fan coils, way better cooling also, plus response time is good. Hate hot bedrooms, once the bedroom is warm its staying that way with UFH.

 

Was this because you had carpets? 

 

I think @Indy has wood and tiles. 

 

Fan cools run at about £300. I reckon it'd work out more expensive than UFH. 

 

 

[Kelvin]

11 minutes ago, Iceverge said:

 

The internal walls aren't too critical if you model them.

 

Of course it's no excuse and frankly accepting any easily preventable heat loss is negligent in my view.  

It’s like the standard 100mm floor insulation. That’s common too and also in our construction drawings until I changed it. I know three people that self-built but were completely led by the architect so didn’t know any better. They would have put more in had they been aware.  I reckon the majority of the Heb Homes only have 100mm. 

Edited December 1 by Kelvin

[Iceverge]

If I behaved like that in my job I wouldn't last a month. 

 

 

[G and J]

1). If I run my ASHP UFH 247 then screed thickness will have no effect on performance and I’ll have reasonably constant room temperatures.

 

2). If I run the heating a bit harder but only in the cheap periods of a ToU tariff like Cosy, I will save money but the room temperatures will vary more than in 1). above.

 

3). If I have a deeper screed then the room temperatures will vary less.

 

Is that correct?

[Iceverge]

1. Yes

2. You can charge the slab on TOU tariffs and allow it to slowly release through the day. Beware this is unlikely to be a successful technique if you don't have a passive class house.

 

3. Jeremy Harris did some numbers on this. Beyond a couple of mm it makes almost no difference. 

 

When it comes to keeping a house warm without the heating switched on it's almost entirely down to airtightness and insulation.

 

Otherwise castles would be notoriously warm.(Spoiler, they're not) 

 

 

Edited December 1 by Iceverge

[Kelvin]

1 hour ago, Iceverge said:

The design appears to have bifold doors and a chimney still. 

 

My advice is to change these to a pair of french doors with fixed side lights and to get rid of the fireplace. 

 

You'll save thousands of pounds and the house will be far less drafty. 

 

 

Solarlux do very good bi-fold doors from what I’ve read. I’ve had two shockingly bad bi-fold doors in previous houses one of which was so bad that the builder eventually agreed to replace it with a French door and side lights. 

[Iceverge]

17 minutes ago, G and J said:

 

 

 

5 minutes ago, Kelvin said:

Solarlux do very good bi-fold doors from what I’ve read

 

 Show me the triple compression seals please!

 

Edited December 1 by Iceverge

[G and J]

43 minutes ago, Iceverge said:

1. Yes

2. You can charge the slab on TOU tariffs and allow it to slowly release through the day. Beware this is unlikely to be a successful technique if you don't have a passive class house.

 

3. Jeremy Harris did some numbers on this. Beyond a couple of mm it makes almost no difference. 

 

When it comes to keeping a house warm without the heating switched on it's almost entirely down to airtightness and insulation.

 

Otherwise castles would be notoriously warm.(Spoiler, they're not) 

 

 

So, the concept enshrined in 2) holds, the question is how much the screed would cool during the off period.

 

I have difficulty finding stuff on here, do you happen to know how to find that?

[Kelvin]

29 minutes ago, Iceverge said:

 

 

 

 Show me the triple compression seals please!

 

I’d need check back on my notes but when I was researching windows the Solarlux SL97 bi-fold was advertised as having triple seals and an air permeability of class 3 (highest being 4) and met the requirements for passive house. I’m pretty sure I got that information from here or a link from here.