Best heating design for a 1930s semi?

[RedMango]

Hi, been doing lots of research for a house we're about to move into and pulling my hair out on what to fit.

The house: 1930s semi, 3 bed, 1 bath (separate shower + Bathtub) its essentially a shell (a rotted falling down shell) 😂 the whole house will be on electric only except gas for heating. I've done a heat loss calc and know what I need per room.

It's me and my wife currently but planning for 1-2 kids in a couple of years and would like a DHW system that could cope with that.

My ideas:
Combi only: Vitodens 100 or 111, with radiators throughout (oversized to run at a DT20) to keep combi low temp/condensing and to future proof for an ASHP.

Combi + Aircon mini split: same as above with combi and radiators except no radiators in living room and master bedroom, where I'll have a wall mounted Aircon unit that heats in the winter and cools in the summer. (I will eventually want to put in Aircon in regardless of setup)

Unvented Cylinder: basically same as 1st option but with a cylinder l.

ASHP + Radiators: Do I just bite the bullet now and get a heatpump, paired with radiators throughout. I like the idea of ASHP so I can get rid of gas supply.

ASHP + UFH: As above with UFH, I'm not convinced the effort involved in putting in UFH in the house is worth it compared to triple panel k3 radiators.

Any input or advice to bare in mind that will help me choose will be much appreciated.

Thanks

 

[ShaunCorbs]

Would go first option and 111 depending on the water main very good for sizing the rads for 50dc flow

Can I ask the Heatloss for the property?

 

[RedMango]

Would go first option and 111 depending on the water main very good for sizing the rads for 50dc flow

Can I ask the Heatloss for the property?

The following is watts & BTUs at a delta of 20, these are going off the measurements I've been given but once I'm in the property I'll redo and expect them to come down very slightly.

Living Room	3749	12786
Dinning Room	2651	9040
Kitchen	2260	7707
Hallway	3767	12847
Bedroom 1	2489	8487
Bedroom 2	1808	6167
Bedroom 3	1356	4623
Bathroom	2485	8473

 

[ShaunCorbs]

21kw ish not really suitable for a heat pump at the current you would need to half the load approximately eg insulation etc

Also would need this to come down as at present to allow for a heat pump in the future your circuits would need to be 42mm and 22mm to the big rads and 15mm to the rest

 

[RedMango]

Any side effect to running 42mm pipe now apart from the extra cost?

Those numbers are the output I need from the radiators sorry. The actual heatloss numbers and far lower. The total heat loss is 6.3kw for the house.

 

[ShaunCorbs]

There the dt50 figures arnt they sorry

So 28mm primary’s required and 15mm to each rad

 

[RedMango]

There the dt50 figures arnt they sorry

So 28mm primary’s required and 15mm to each rad

Perfect that's what I had planned for, and presuming an ASHP is viable at 6.3kw heat loss if I decide to go that route later on?

 

[ShaunCorbs]

Perfect that's what I had planned for, and presuming an ASHP is viable at 6.3kw heat loss if I decide to go that route later on?

Yes more on the line / idea on heat loss I was thinking

Eg vaillant arotherm plus 7kw

 

[Murdoch]

I would have a hot water tank with an immersion.

So when the boiler breaks down, you'll still have hot water and if you later install PV then you can have a divertor to the immersion fitted

 

[RedMango]

I would have a hot water tank with an immersion.

So when the boiler breaks down, you'll still have hot water and if you later install PV then you can have a divertor to the immersion fitted

I will be getting PV but in a few years, I will probably change to an ASHP in a few years as well I'm just not quite ready for it yet.

 

[Last Plumber]

Heat loss for the house sounds low to me. What temperatures did you use for inside and out?

 

[RedMango]

Heat loss for the house sounds low to me. What temperatures did you use for inside and out?

-0.3c and 19c

I'm in Devon by the sea and it hardly drops below -1 for any period of time. Especially a time when we'd want heating. I also prefer to be on the cooler side hence the 19c rather than 21c as the norm

 

[Last Plumber]

-0.3c and 19c

I'm in Devon by the sea and it hardly drops below -1 for any period of time. Especially a time when we'd want heating. I also prefer to be on the cooler side hence the 19c rather than 21c as the norm

I see. I must be missing the point on your calcs/figures then. How can you have those figures for radiator outputs at over 20 Kw yet have a heat loss for the whole property at 6.3 Kw?

I have obviously not seen the house but I have seen plenty of pre-war 3 bed semi's and I would expect the rad figures you gave to be nearer the mark.

Don't think I am having a go at your maths, it just doesn't make sense and I wouldn't want you to make a mistake with figures that could cost you money or take you down a path that might not work out as you expected.
Your living room and dining room are over 6.3 Kw.

 

[Last Plumber]

Going back to your initial post:

I would advise you to install an unvented cylinder and 24Kw Vaillant boiler (624) with senso controls (true weather comp, not internet based). I am going off your room heat loss figures for the boiler size (cylinder taken into account too). Insulate the loft well (taking into account the necessary ventilation).

You need to make sure that your water main is up to the job for an unvented cylinder.
Don't be tempted to oversize it as there is no need to heat hot water just for the hell of it.

 

[RedMango]

I see. I must be missing the point on your calcs/figures then. How can you have those figures for radiator outputs at over 20 Kw yet have a heat loss for the whole property at 6.3 Kw?

I have obviously not seen the house but I have seen plenty of pre-war 3 bed semi's and I would expect the rad figures you gave to be nearer the mark.

Don't think I am having a go at your maths, it just doesn't make sense and I wouldn't want you to make a mistake with figures that could cost you money or take you down a path that might not work out as you expected.
Your living room and dining room are over 6.3 Kw.

Those numbers you're referring to is the output I require from a radiator at my lower delta. The 6.3kw is the heat loss for the house

 

[Last Plumber]

Those numbers you're referring to is the output I require from a radiator at my lower delta. The 6.3kw is the heat loss for the house

Yes I know what you're saying and that is why it doesn't make sense. Maybe there's a misunderstanding somewhere?

If you require an output from a radiator or any other heat emitter, it is usually to make up for heat loss from a room or building and to raise temperature to a level of comfort for the human body.

We are obviously at cross purposes somewhere but so long as you know what you mean it's fine.

 

[Chuck]

The 6.3kw is the heat loss for the house

Unless it's had some exceptionally effective insulation added recently, I also find it difficult to believe this the correct figure for a 1930s house with three bedrooms and two receptions. How was it arrived at?