Hi everyone,

I last frequented this forum a few years ago. We had been trying to build an eco house on the outskirts of Bath but were ultimately thwarted by the planners. After sulking for a while we have turned our attention to a new project and need to get some up-to-date advice from you all. I have searched the forum for various things but lots of the posts are quite old.

We are in the process of buying a grade II listed farmhouse with outbuildings and 3-4 acres of land.

We need advice on the following subjects which are explained better below the list:

1 - Heating for the house.
2 - Solar heated hot water.
3 - Insulation for the house.
4 - Solar PV.
5 - With all the above considered we need to install a brand new kitchen (there isn't one to speak of) and so need to choose an oven.

1 - Heating the House.
With our eco-house and land our plan was to grow a coppice and use a Windhager log gasification boiler and accumulator to heat the house. Since then life has got a lot busier with another little mouth to feed and entertain and business has increased hugely - we run a design studio from home, so little spare time.

I would like to know whether it is now practical to install solar panels (something we would like to do) and to put in electric underfloor heating in the house. This would be minimal or no involvement from me and the house would be heated by electricity that we produce and sell to the grid. The flooring throughout then house is wooden floor boards - very old but very good condition - so I would imagine some underfloor heating matts going under carpets and sitting on top of some sort of reflecting/insulating matt so that all the heat goes into the room and not into the floor boards.

Are there any other electrical heating solutions to consider?

Whisper this one - Heat Pump... are we allowed to mention these here nowadays? We have a large south facing garden, not to mention a 3-4 acre paddock. We could install a ground source heat pump powered by the solar panels. This could put the heat into the central heating system that is already there. I'm guessing we'd need some sort of accumulator installed.

Does anyone have any advice on modern GSHPs and their running costs?


2 - Solar heated hot water.
Solar Thermal panels for hot water - How close do these need to be to the tank to work efficiently? We will not be allowed to install them on the farmhouse roof but there are other roofs nearby that would be suitable but I am concerned that too much heat would be lost in the transfer to the tank, unless the tank is moved too.


3 - Insulation for the house.
We have to take the roof off the house and re-baton. In the process we will fully insulate the roof and attic space as it is not needed for storage.

The house is very solid and sound with thick external walls. The house dates from about 1800. Should we look at putting a layer of insulated plaster board on the walls inside the house or is this not worth it? If yes, what products should we look at?

The windows are all single pane. We intend to install secondary double glazing. Does anyone have any advice on this and is there such a thing as secondary triple glazing yet and would it be worth it?


4 - Solar PV.
We will miss out on the <1st August FIT rate. We will need to get the house roof done and probably install secondary glazing to improve the EPC to a band D anyway. I think we will be in a position to install solar panels onto one of the barn roofs sometime around December.

Can anyone recommend an installer/company near to Bristol and Bath in the South West? I would like to hear from people who have had good and bad experiences and you can send me a private message, whisper it or email (tom at grizzlyhippo dot co dot uk) about this so that no company names are mentioned in this thread.

How much money should we be allowing for a 4kW or 8kW installation nowadays?

Ideally I would like to install about 6-8kW of PV but understand that you are then put into a lower FIT bracket. Would it make sense to install 4kW using an approved installer and then put the rest up ourselves and wired into batteries for daily use? Is this even possible i.e. if the batteries run down the system needs to swap over to using mains.


5 - Kitchen oven.
Right, now the important bit. We're not going to have much, if any, money to play with after purchasing the property and doing the roof. We definitely won't be able to install all of the above in one fell swoop. However, we need to get our energy plan in place straight away as we need to install a brand new kitchen.

Ideally, being an old farmhouse, we would like a range cooker. I grew up in a house with a solid fuel Rayburn and like that central homely feeling that the Rayburn gave, the kitchen always being the hub of the house. We have looked at the Rayburn range and see that you can choose from solid fuel, oil and electrical versions. We would like an cooker/range with two ovens.

Does anyone have experience of the electric Rayburn and can they give us comments.

If we are going to install solar PV my gut says that it makes sense to have an electric oven. We could always have an oil Rayburn (the current heating system is oil fed) and use it for just the cooler months, having a normal electric oven for the summer months. This might be a bit extravagant though. Any thoughts on this?

Also, are there any other efficient range size cookers (electric or oil) that we should consider?


I know that's a lot to digest but look forward to your replies. If it's too much in one post I might break it up into sections and re-post.

Many thanks,
Tom (GrizzlyHippo)

Before you can think of anything you need to do a detailed energy loss audit.
Then work on reducing your demand.
Nothing wrong with using PV to heat the place with, but I suspect that it is not in the least bit cost effective.
I think you could fit up to 4.5 kWp of panels on a 4.2 kW inverter (limited to 3.68 anyway) and generate nicely.
Batteries will be a huge drain finacially and you may be better off just heating water with any excess.
Bit late at night to think about the rest, but insulation and airtightness are the things to think about.
Woodburners of any sort are the last thing you need to think of at the moment.

Our firm is a member of the design team renovating a Grade A listed (NI) stately home and have the same issue of remoteness of a suitable roof to the hot water load.

The approach is to use PV dedicated to an Ecocent or equal ASHP cylinder. The PV array is sized to match the annual electrical consumption, hence can be classed as a zero carbon DHW system. The distance from the panels to the point of use is therefore not an issue.

For information, the rest of the environmental strategy is as follows:

Walls: 900 thick with lath and plaster, U-value 0.9 w/m2K - no upgrade proposed (or allowed).

Windows: draught stripping only - the shutters and heavy lined curtains are closed in winter. This is nearly equivalent to triple glazing. Have you got shutters that can be recommissioned?

Floors: ground floors to be insulated in mineral wool between the joists, retained using breather membrane rather than the usual netting, to reduce draughts through the floorboards. Not all rooms are being fully insulated due to the importance of the inlaid floors on some rooms.

Roof: previously insulated 270mm mineral wool but will be increased to 400 and cross-laid to reduce thermal bridging at joists.

Heating: already converted to woodchip and supplied from local willow coppice. Existing cast iron rads to be supplemented with plate type underfloor heating in rooms where comfort is an issue. Zone control is being introduced (30 zones) plus changing main heating pumps to A rated inverter drive units.

Lighting: historic fittings to be refurbished and LED bulbs to be used where practicable.

Rainwater / spring water harvesting to supply all WCs and for watering of plants.

We are limited to what can be done with walls, windows and some floors for conservation / historic heritage reasons.

I'd have thought the first thing to do would be to get the CO and planners views on what they might allow. I suspect the options for improving the insulation level are going to be quite limited by the listed status and I doubt whether the house could ever be made to be particularly energy efficient; it might possibly be able to reach the sort of thermal performance of a house built 50 years ago at best.

As ST says, an energy audit is really the best way to start, working out the current energy usage and the likely energy usage after you've done all the insulation and airtightness improvements that might be allowed. That'd then give you a good starting point for looking at the best way to heat the house and DHW, within the restrictions that you will have from the building's status.

Having lived with Rayburn for around 5 years I can say with certainty that it is the singularly least green appliance (other than, perhaps, an open fire) that I've ever had. The fuel consumption has to be experienced to be believed! They are great for cooking, and do definitely add appeal to a kitchen, I agree, but there's no way I know of to make them even vaguely efficient, plus they tend to over-heat the kitchen (and house) during the shoulder months of the year and you need an alternative cooker during the summer when it gets too warm to even entertain the idea of having the Rayburn on. They also have a fairly high air demand, which increases heat loss from the house from ventilation. AFAIK they don't normally have an external air intake, so they draw a fair bit of warm room air up the flue.

You could sort the airtightness out from outside, new coat of render, or new pointing whichever you have, trying to do it on the inside is a nightmare, between floors etc..
We chose only to insulate the inside of our slate walls in the bathroom where you really feel the chill, otherwise UFH from log boiler, and woodburner in the snug..ie decamp to the west wing in winter!
Run the calcs and you might find the log boiler is necessary..as much a lifestyle choice as anything..
UK range cookers, ie esse rayburn aga are inefficient beasts and produce high emmissions, reason enough for most people on the forum to hate them, however you can install a masonry range which operates like a gasification boiler, high temp efficient burn, storing the heat in the masonry body of the range rather than in water..you can also incorporate heated seats!
Electric underfloor heating..jury out on that, I think ok for occasional use areas, ie bathroom but you wouldn't want to sit or sleep over it!

I agree - it's a despairing time, for uprating Listed Buildings. This will change, but you'll suffer much frustration if attempting it now. Leave it to some other hair-shirty person for the time being, return to that gorgeousness once it's safe!

Posted By: WillInAberdeenElm

You still got elm in Aberdeen? Or is it just the young trees, which catch the bug and die soon enough?

Posted By: fostertomas Agas have much greater thermal capacity, can store enough heat from overnight off-peak charge-up

SHC of Iron is 0.45 J.g^-1.K^-1, air is 1.
So the air in your house may be better, just depends how heavy an Aga is and how large your is.

Hi,
The modern oil fired Rayburns simply have a pressure jet unit in the fire box so aside from the horrendous fuel consumption you have the noise of a jet engine in an iron box reverberating up the chimney. Ok not all are bad but it can be a shock when it starts up – particularly conversions where it has been shoe horned in as an extra. Only the newer models were designed this way. The older solid fuel units when converted to oil use a vapour pot burner and wick and are silent. These still use quite a lot as they are continuous burn, you can of course wind it up and down, but you need to start planning Sunday lunch around Thursday as slow to respond. If left on the lowest setting continually it will provide a mass of background heat which was supposed to be in a draughty farmhouse kitchen not a renovated property.

Years ago one of our solid fuel Rayburns did about 5 months continuous without the fire ever going out.


Cheers, Mike up North

Posted By: fostertomYou still got elm in Aberdeen? Or is it just the young trees, which catch the bug and die soon enough?

Still the old trees, the bug has travelled up the country and arrived here about 5 years ago, so we have a lot of dead elm that has dried for 5 years now. Still doesnt burn very well. Couldnt get sawmill interested as theres so much dead elm about and theyre not very straight.

Interestingly some of the Wych elms seem to have survived.

Thanks very much Roger. I wish I could have seen that two years ago though.
It certainly makes my spreadsheets for our recent restorations look a bit better.

I've been seriously suspecting for a while now that rubble walls like this performed much better than a 600mm thick lump of limestone but couldn't find any hard numbers to back this up. We have been wondering about one more heatpump to finish things off but it would be a retro fit to a building with plain rendered stone walls that currently has an oil boiler - I can't face the work/time to redo the envelope again.

It was looking barely feasible before this data but I will look again more closely.

The "best" way to use the electricity IMHO is to maximise the carbon savings they offer, which is *not* to waste it in electric resistance heating in any shape or form where one kWh of electricity makes only 1kWh of heat, if possible.

Much better to use that electricity with a heat pump where you can get several kWh of each of each kWh of PV generation, or push it back into the grid where it displaces fossil-fuel generation for someone else similarly.

Rgds

Damon

PS. If you don't buy the carbon argument the money argument for the fuels by the kWh for heat is fairly close.

John - Sorry, just had to laugh.

<blockquote><cite>Posted By: GrizzlyHippo</cite>
I know this is a misnomer but are there any electric space heaters of any description that might be viewed as efficient, especially as we will have our own PV? I seem to remember murmurings of some sort of electric radiator technology a couple of years back but I wasn't interested enough to take notice at the time.

Cheers,
Tom</blockquote>

Electric resistance heating, be it fan heaters, oil filled radiators, direct electric convection or radiant heating, is all 100% efficient. The nature of electric resistance heating is such that all the supplied power gets turned into heat.

Heat pumps, however, can appear to have an efficiency that's greater than 100% (although that's not technically correct), in simple terms of comparing electrical energy in to heat energy out, typically they will deliver around 2 to 3 times more heat energy out than electrical energy in, making them only a little less effective than gas in terms of CO2 emissions and running cost.

If you want PV to offset grid imports for heating/DHW then a heat pump is probably your best bet, as it'll use a lot less electricity than direct resistance heating. The heat pump will still need the grid to act as the storage buffer for the PV generated power, at least for space heating, but it's probably the best you can do.

Or do the same thing non electrically, capturing solar as very low temp heat (therefore v high efficiency - much better than normal wet solar and incomparably better than PV), stored in mass.Forget the bad winter's days - there's enough sunny ones, even Dec/Jan, with adequate insolation, provided it can be stored to serve the bad days.