Suggestions for heating a large detached period property

highdef

I'm renovating a large detached period protected property at the moment and building an ICF extension on the northeast end of the house. The house is about 200 years old and is located in the midlands. The current/original part of the house is about 5,000 sq ft, over 3 levels. Currently there is no roof insulation but that will not be the case post-renovation. All but a central room in the bottom floor will have underfloor heating. Ideally, I would like to heat the upper 2 floors with radiators, less interference with the current original wooden floors being a major factor. I have already purchased antique oversized cast iron radiators for the middle floor which were salvaged from another large property. They are far bigger than any sort of modern radiator and have very large surface areas. Ceiling heights range from 3.4 to 3.8m. Walls are close to 1m thick, a bit thinner at windows.

The extension is a little under 2,500 sq ft, also on 3 levels. Part of the renovation will result in the house having slim line double glazed windows (some replacement windows which are made of teak) with most being restored pitch pine. The extension will be mainly triple glazed, with just a couple of double glazed doors, due to their size.

Ideally, I would like to go down the ground source heat pump route, if possible. There is only single phase electricity available and there is plenty of room for a horizontal loop system. I would like to try keep away from fossil fuel heating as it is essentially a new heating build so starting off with a technology which is planned to be phased out would seem like an oversight. Also, there may be occasions when there will be high demands for hot water, as much as two baths and two showers calling for hot water concurrently……so this would need to be doable too.

The question is, is there a suitable solution that won't require a second mortgage to pay for? Any other helpful tips on best hardware and/or best companies to deal with, both for installation and after care service would be very much appreciated. Plus anyone in the business is welcome to reply here too, or by a PM if preferred.

Lenar3556

My initial thoughts is that a heat pump is going to be very challenging to implement given the building’s significant heat requirement, coupled with only single phase power.

Oil or gas is going to be much more practical. However I would consider sizing the radiators and cylinder to suit a heat pump system at a future date.

You could conceivably combine a smaller heat pump supplemented with oil/gas.

If you wanted to introduce renewables you could also consider HVO fuel with a modern oil boiler. It is arguably carbon neutral.

L1011

Would any heat pump (groundsource or air source) be able to heat cast iron radiators anyway? They struggle with steel; plenty are sold as being fine with steel radiators but I've been in some very tepid houses.

highdef

Thank you both, much appreciated. Another thing I've thought of is a kerosene boiler for the middle and top floor of the main house (radiators) and geo-thermal for the basement level and modern build extension (UFH), in essence two different heating systems……however if it were possible for them to either work in tandem or have the option to run the entire house solely on either system in a fault scenario with one of them providing all heat/hot water, even if it resulted in it being a bit cooler than desired until a fault is fixed, that could be doable too.

There will also be a kerosene Aga in the kitchen and kerosene stove in a bedroom, both at basement level of the main house so an oil tank will be fitted in any case.

Sonic the Shaghog

I've read this before as well. The newer lighter rads seem to be all that really works well with them. I'd do my research on a HP with the rads you've mentioned

Theanswers

I'm looking into this myself for a similar property. I'm going with large solid fuel burner with 1500 to 2000 litre buffer tank in a out building. I have friends and family with similar properties and sware by it.

The system would also have a backup oil burner.

Calahonda52

OP: Starting point is a heat loss calc by room

has the buffer tank been sized or is it just a TOTT calc

Dont Be at It

I know of a couple of horror stories where people installed air to water heat pumps in red brick period houses in Dublin. Ended up with massive heating bills and the house still wasn't that warm.

Air tightness and high levels of insulation are realistically needed for heat pumps. Both of which are hard to achieve in old houses (without spending a fortune).

I'd advise getting professional, INDEPENDENT advice anyway. Could be the best money you ever spend. Best of luck with the project - sounds like some house!

Lenar3556

https://www.boards.ie/discussion/comment/122448255#Comment_122448255

It would heat them the same as a steel or aluminium radiator, just it will take a long time for them to heat up (and cool down) And they would need to be sized for the room with a flow temp of 43 degrees approx.

It’s inadequate sizing that is the issue in a lot of these retrofit cases. The rads were sized with flow temps of 70 degrees in mind and the heat pump then supplies as 43. You are talking less than half the output at heat pump temps.

Lenar3556

https://www.boards.ie/discussion/comment/122449498#Comment_122449498

I’m not yet a huge fan of heat pumps, but the narrative that they need air tightness and very high insulation levels is a little bit of a misnomer.

Of course any building will benefit from better insulation, but in that regard a heat pump is no different to oil, gas or solid fuel. A gas boiler will use much less gas, and you will need a smaller boiler if the place is well insulated.

The same is true of a heat pump. The problem in most cases when you hear of very high heat pump running costs is that;

1. The emitters are undersized and the heat pumps flow temp has been turned up by the customer or installer to compensate. These higher temps are outside of the capacity of the unit to reach within the designed COP range and often the boost element(s) are operating continuously.
2. The heat pump itself is undersized.
3. It hasn’t been commissioned correctly, particularly the flow/return differential temp.

Install a suitably sized heat pump into a house with suitably sized radiators/underfloor it will work just as well without adding additional insulation.

Dont Be at It

https://www.boards.ie/discussion/comment/122450059#Comment_122450059

In theory you might be right but not sure about in reality. Heat pumps heat much more slowly than the quick blast you'll get from oil/gas heating rads. If a building doesn't have high levels of air tightness the heat pump can struggle to keep up.

Rows Grower

Any money you spend on insulation will be an investment, especially under the underfloor heating, you only get one chance at doing that properly.

Are you insulating the walls before fitting those huge rads? I presume the rooms are big enough, sounds like a massive job of work.

Best of luck with the project but you're going to need a right handy few bob to complete it without a mortgage.

Lenar3556

https://www.boards.ie/discussion/comment/122450304#Comment_122450304

Not really - It’s a question of sizing. A heat pump heats water to its set point reasonably quickly, not remarkably slower than an oil or gas boiler of equivalent output.

The difference is the flow temperature will give you less than half the output from a radiator than you were getting on oil, so the radiator needs to be much larger to “keep up”. (Or fan assisted for example)

Calahonda52

Similar sorts of issues arise when old oil gas boiler are replaced with condensing , shying flow rates form maybe 85C down to 55C

Airtightness is the key piece here as if you do a room by room heat loss calc as part of the energy balance math, without knowing what the heat loss via the real ACH is, then in terms of just energy loss through the fabric, the rads and HP might be line ball, but once the warm air is lost through high ACHs then the client won't be either warm or happy (and as the great Frank Carson joked: if you are not Happy, which one are you!)

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Doc, Grumpy, Happy, Sleepy, Bashful, Sneezy, and Dopey.

Dont Be at It

https://www.boards.ie/discussion/comment/122450552#Comment_122450552

You'd get a lot of fills of oil for the cost of putting in a viable heat pump system I'd wager.

Anyway, as I said a good independent consultant is worth it in a project like this one.

Calahonda52

1000 litres of oil= 10,800 kWh *.85 =

9180 kWh at say 1 euro a litre or 10 cents a kWh = euro 918

9180 kWh at COP of 3.5 = 2622.85 kWh at night rate of 18 cents = euro 472

Lenar3556

https://www.boards.ie/discussion/comment/122451260#Comment_122451260

Condensing boilers can run at similar temps to standard efficiency boilers without impacting efficiency.

It’s the differential temp between flow and return that is significant to enable condensing.

Lenar3556

You would, and there are practicalities to consider when it comes to retrofitting larger heat pump systems in domestic houses;

1. It’s a significant investment, and before you even start, it begs the question of shouldn’t some or all of this money be spend on insulation instead? It is usually a much better investment.
2. The radiators may need to be double the current size - is there space? Will it impact negatively on the function of the room?
3. Power requirements are significant, most domestic supplies will be inadequate.

Lenar3556

https://www.boards.ie/discussion/comment/122451887#Comment_122451887

Are COP’s of 3.5 actually sustainable over the course of a year?

Calahonda52

https://www.boards.ie/discussion/comment/122452037#Comment_122452037

1: the energy efficiency of condensing boilers is up to 99% efficient while non-condensing boilers are only up to 78% efficient.

2: if the return temp is not low enough it won't condense so its not the delta T

Calahonda52

https://www.boards.ie/discussion/comment/122452157#Comment_122452157

Seasonal COP of 3.5 very doable with right design, might dip a bit with -12 C for day or so

Grassy Knoll

https://www.boards.ie/discussion/comment/122450059#Comment_122450059

Hi I think you are correct, there is a lot of vid material from credible sources on uTube where air to heat source pumps have been installed and the properties are not particularly well insulated etc.

Tow

In a similar type of house i have seen two condensing (gas) boilers used. A smaller capacity and a large capacity. The small boiler (basically) runs all the time and larger boiler operates more traditionally, on a timer. This keeps a minimum temperature with the small boiler 'condensing' all the time to give max efficiency. The assumption is you can afford to heat the house, because with this system someone messed with the controls during Covid. When the meter was eventually next read the gas bill was for well over 10K.

highdef

https://www.boards.ie/discussion/comment/122449498#Comment_122449498

Thank you. I've sent a mail to one of the Technical Advisors from the SEAI registered list so will see how that goes.

highdef

https://www.boards.ie/discussion/comment/122450417#Comment_122450417

I can insulate the interior walls on the bottom level (due to the lie of the land, it's basement level at the front of the house (with a moat type thing between the house and the land…..and ground level at the back) as there is no coving at the tops of the walls…….but of course, there are no rads going in on the bottom floor as it's going to be UFH there. The other two levels have historic coving and this can't be touched so installing insulation would compromise the aesthetic appearance so would not be permitted. Would the sheer thickness of the walls help in terms of insulation? The house is about 200 years old and the exterior walls are about a metre thick (slightly less at windows). I've looked at some Edwardian and later Victorian homes in Dublin and the walls are far shallower so I'm thinking the thicker walls would be a better thing, in the longer term?

I have a mortgage, specifically to renovate the house but my funds are obviously finite!

Furze99

500 sq metres in old part and an extension? Goodnight - if you can afford to buy and renovate such a gaff, heating bills by oil or gas should be a dolly! There's such a period house near us and the people live in a basement part which is heated, the rest of it is just kept dry with a low level of heating to keep damp at bay. That's likely the practical approach unless you're Flatley :)

Lenar3556

https://www.boards.ie/discussion/comment/122452233#Comment_122452233

1. Why up to 78% for non condensing boilers? There isn’t necessarily a ceiling. It came down to boiler design. The old Grant Euroflame (standard efficiency) for example which sold very well in Ireland from the late 1990’s on had a seasonal efficiency of over 85%.
   
2. This is true, but the specific parameters depend on the boiler. I was responding to your previous post that new condensing boilers would have flow temps of 55 degrees to radiators and that output issues arose. That wouldn’t be typical, or necessary to maintain that low a flow temperature. Most condensing boilers are designed to perform at the stated efficiency whilst maintaining flow temps of 70degrees. So they are a direct replacement for older (non-condensing) models.

highdef

https://www.boards.ie/discussion/comment/122453123#Comment_122453123

I'm no Flately, that's for sure. Sold last house at a great price so could buy the virtually derelict house outright as a long term project with an aim to have it earn money back in the future as a high end B&B. The pair of us have fairly regular full time jobs and we're not wealthy, we're just tipping our toes in the water and are on the biggest adventure of our lives. No kids helps!

Dont Be at It

https://www.boards.ie/discussion/comment/122453091#Comment_122453091

Just on the walls with the coving - you may get away with stripping the old plaster off below the coving (leave coving intact) and then insulate with diathonite plaster insulation. Depending on the design of coving you might be able to get 25-40mm thickness on. Make sure there's no dampness.

CelticRambler

https://www.boards.ie/discussion/comment/122453091#Comment_122453091

Would the sheer thickness of the walls help in terms of insulation? The house is about 200 years old and the exterior walls are about a metre thick (slightly less at windows). I've looked at some Edwardian and later Victorian homes in Dublin and the walls are far shallower so I'm thinking the thicker walls would be a better thing, in the longer term?

Bascially, no. Unless the walls are insulated externally, the thickness just stretches the thermal gradient between inside and out over a longer distance. If it's freezing cold outside, you're as likely to get condensation on those walls if the inside is (excessively) heated as you'd get if they were only 20cm thick. I have uninsulated 70cm stone external walls in part of the house - north-facing and south-facing and they're all going to be drylined when that part comes up for re-renovation.

Ceiling heights range from 3.4 to 3.8m. 

On a separate point (which no-one else has mentioned) you'll also be aware of stratification of heat layers within those high-ceilinged rooms. Again, I have rooms with similar ceiling heights and there are times when I wonder why I don't hang chairs from the ceiling instead of having them on the floor! This is particularly noticeable around Christmas/New Year when I'd be hanging decorations and getting the house warm for visitors. With a wood-burning stove going full pelt, you might still need a hat and coat if you were sitting in the far corner, but you'd be sweltering after putting up the first set of garlands. That high-up heat goes on to create uncomfortable draughts when it cools against the uninsulated thick stone walls and heads back to the stove at ankle-level. Underfloor heating is better in this regard than extra-hot radiators, as you're heating the whole room, instead of sending a column of air up the wall to heat the coving and ceiling rose.

Lenar3556

https://www.boards.ie/discussion/comment/122453712#Comment_122453712

Potentially an improved solar gain from these thick walls? they would likely have significant heat capacity.

highdef

https://www.boards.ie/discussion/comment/122453712#Comment_122453712

Cheers for that…..very helpful indeed. One slightly good thing is that the extension will cover the entirety of the NE facing external walls, they will then become internal walls so one less section to need to deal with.

@Dont Be at It , thank you for that very useful information about stripping the old plaster off below the coving and then insulating with diathonite plaster insulation. This particular method and product is not one I've heard of but I will certainly look further into it. The lime plaster on the internal walls is very thick so this could be a viable solution. The original drainage surrounding the house is excellent (have found Roman drains around the house) and dampness is not an issue, bar one section at the front of the house but this is due to the front steps needing resetting and a DPM installed, which will be done in due course.

highdef

During the summer, yes…..but during the colder months, it would be minimal, when it is needed most. However, the entire NE facing external wall will become an internal wall when the extension is complete so that's a big section of cold dark wall eliminated from the elements.

CelticRambler

https://www.boards.ie/discussion/comment/122454036#Comment_122454036

My experience is that any solar gain is felt only on the outside after the sun has gone down. My south-facing walls will regularly get 50°C+ of direct high-intensity sunlight (make that 60°C this last week) for about six to eight hours in the height of summer. In the evenings, that heat escaping keeps the adjacent area at about 10° higher than the space behind the house.

However, as long as my (Irish) visitors do what they're told and close the shutters by eleven a.m. the temperature inside, in those rooms, won't go above about 20-25°C (less if they also did what they were told and left all the doors and windows open the previous night … :-p ). That's great for no needing air con, but no help in the winter when I get far more "solar gain" from the sun shining through the windows.

the extension will cover the entirety of the NE facing external walls, they will then become internal walls so one less section to need to deal with.

This will make those walls far more useful as a "heat source" and somewhat mirrors what I'm doing with my current project. If you can raise the temperature on both sides of the wall, eventually the whole wall will absorb and store that heat, and mitigate any drop in temperature one on side or the other. This is where lower-temperature UFH (+/- heat pump) comes into its own - provided, though, that these are rooms that are going to be in use all the time. It'll be of no real benefit if, for example, it's a reception room that's only heated/occupied once a week.

Idbatterim

assuming you arent on a natural gas line?