Seeking advice wrt modernising the heating system on a 100+ year old property.

[kentar]

My house is a 4 bed semi, early 1900's and is solid brick construction. Can't say how old the plumbing system is, but safe to assume pre 80's. An ASHP will be replacing the now defunct gas boiler and an unvented 200/250l hot water cylinder will also go in, but i'm unsure of what to do about the heating system. 

 

The current system uses a non-condensing boiler with a vented hot water cylinder. It lacks hot water pressure. The shower is fed using a pump to combat this but it runs the 140l tank dry within 10 mins.

Half of the rads need replacing as they're extremely old. One rad is definitely full of sludge and barely gets warm even after a flush. The only saving grace is that all pipes to rads are 15mm.

 

I've heard people claim that underfloor heating is best with ASHP, but also that it's difficult to retrofit to older properties. 

 

1. Should I go for underfloor heating or radiators?

2. Can radiators be changed easily to underfloor heating at a later date, or does it need to be designed for it from the off?

3. Is there a third (or fourth) option?

4. Any other considerations?

[Dillsue]

If your boiler is now defunct, my advice would be to have a look on ebay or marketplace and get a secondhand replacement to repair or replace what you've already got. That will buy you time to answer all your questions and work out what you need/want rather than rushing into throwing an ASHP under pressure to get the heating back on. 

Edited Tuesday at 22:41 by Dillsue

[kentar]

Understandable, but i've got fan heaters as backup and the immersion heater is taking care of the hot water. I'm pulling the trigger by the end of the month, which I think is ample time to decide on a plan.

[Dillsue]

8 hours ago, kentar said:

I've heard people claim that underfloor heating is best with ASHP, but also that it's difficult to retrofit to older properties. 

 

1. Should I go for underfloor heating or radiators?

2. Can radiators be changed easily to underfloor heating at a later date, or does it need to be designed for it from the off?

3. Is there a third (or fourth) option?

4. Any other considerations?

A large emitters surface area is what works best with a HP so that it can work at low temperatures. UFH gives a large area without being intrusive but radiators can give a big enough surface area too. Retro fitting UFH is more involved, intrusive and costly than radiators so it's up to you what you go for depending on your preference for the type of emitter versus your budget. If you've already got usable plumbing for radiators then that's a plus for rads.

 

Hopefully you already know what's involved in installing wet UFH so you'll appreciate that it's pretty disruptive to install. If youve sized your rads to operate at low temperature, the plumbing involved in swapping from rads to UFH is a small proportion of the work to install UFH.

 

The other consideration is to look at your insulation and draught proofing before you spec a new heating system.

[JohnMo]

Cylinder for a 4 bed do 250 to 300L

 

1. Unless mad set on UFH don't, do radiators with a  design temp of 35. You will get push back from installers, but your running costs will be very good.

2. No

3. Wall mounted fan coils, these would give summer cooling as well as heating and smaller than 35 Deg radiators. But more expensive.

 

A2A heating system (Aircon) would replace the whole wet system, but you would need to think about DHW heating as separate thing.

 

4. Costs

Do not accept a system design that includes 

Glycol - it requires a higher flow temp and more pumping power to move it about the system compared to water.

Buffer, volumiser is ok to achieve 20L water per kW output of heat pump.

Thermostat in every room, so a zoned system - needs to be fully open single zone ideally.

Third party control, need to manufactures controls only.

 

Suspect most your plumbing will get replaced.

[richi]

I second @JohnMo’s suggestion: Consider air-to-air. I’ve recently installed a pair of 5kW Toshiba Haori splits—one at each end of the house. So far so good and my modeling suggests it'll cope with the coldest winters we've seen in this old house since we moved in 10+ years ago (and summer cooling without having to worry about condensation problems with fan coils).

 

I expect to be a bit better than cost neutral, but even if I don't save money, I still needed to replace the 50-year-old boiler, the oil tank and a couple of manky rads.

 

Caveat: I’m replacing an oil fired system, which is roughly 150% of the running cost of gas.

[marshian]

46 minutes ago, richi said:

 

I expect to be a bit better than cost neutral, but even if I don't save money, I still needed to replace the 50-year-old boiler, the oil tank and a couple of manky rads.

 

Caveat: I’m replacing an oil fired system, which is roughly 150% of the running cost of gas.

I was under the mistaken belief that oil fired boiler heating was the cheapest of the fossil fuels?

 

I’ve always assumed the downsides were storage, higher cost of oil boilers and paying up front for the oil (compared to paying after usage for gas)

 

clearly I was wrong?

 

 

[richi]

Oh, wait, I think you're right, sorry. My memory of the gas price is bogus.

A good price for bog standard 28s kerosene delivered is 55p per litre. A litre has a touch more than 10 kWh of energy. however, the best oil boilers are less efficient than the best gas boilers, because they don't modulate.

[Gone West]

1 hour ago, richi said:

Oh, wait, I think you're right, sorry. My memory of the gas price is bogus.

A good price for bog standard 28s kerosene delivered is 55p per litre. A litre has a touch more than 10 kWh of energy. however, the best oil boilers are less efficient than the best gas boilers, because they don't modulate.

An oil boiler is cheaper to run than a gas boiler. There are also modulating oil boilers.

 

https://sapphireheatsolutions.co.uk/

 

[Beelbeebub]

Oil boilers are currently cheaper to run than gas but the price tends to be more volatile when world events happen around oil producing nations....

 

 

[JohnMo]

But the OPs non condensing one won't be cheaper than anything to run. Plus it's at least 30 years old.

[marshian]

3 minutes ago, JohnMo said:

But the OPs non condensing one won't be cheaper than anything to run. Plus it's at least 30 years old.

 

Wasn't the point being made........................