The Accidental Smallholder Forum
Smallholding => Renewables => Topic started by: goosepimple on August 15, 2011, 10:53:44 am
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Anyone out there used a heat recovery system in an old house? We are presently reviewing all our heating / hot water / cooking arrangements as we are gutting the house and want to get rid of our lpg boiler. We have a water wheel, a small windmill, several woodburners and an aga at our disposal and are relining our walls and attic with insulation. We are also planning solar panels - in other words we are doing all the things we should be doing(so please don't post with how we should do it, we do know this bit) but we haven't ever installed a heat recovery system. Anyone know if they work reasonably well, how expensive have you found them to install, worth the hassle or not, that sort of thing etc. Views appreciated, many thanks.
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Do you mean a heat recovery ventilation system? (i.e. extract warm damp air from say the bathroom or kitchen, and use it to heat incoming fresh air from the outside?). If so, I did get quotes for one recently, but they were very expensive (£2K!), and I think probably ineffective in our house, given how much air is already coming in and out via draughts.
Since budgets are tight at the moment, we're going to finish doing all the non-sexy stuff first, like draught proofing and insulation, and will then come back to the ventilation system at a later date perhaps.
One thing I did see, was a system which also incorporated an air source heat pump. Basically it added an extra stage to the standard heat recovery ventilation system, thus the incoming air was heated to higher than the temperature in the room, by extracting the heat from the outgoing air. Again, this wasn't cheap, but it sure was clever!!
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Womble is right - heat recovery systems rely on controlled ingress of ventialtion air - older houses tend to not be "airtight" enough for them to work well. Heat pumps are clever too, but relatively expensive, require electricity as their "fuel" and won't work with any old radiator system.
I'm sure you have though about this a lot, and its great to hear what you are putting into action, but it never hurts to review whether you are putting your hard earned cash ito the right places.
One widely accepted philiospohy on cost-effective energy strategy is be lean, clean then green. In other words, reduce your energy consumption first, then be more clever with the energy you are using (e.g. using heat recovery - which is moving energy from one place to another) and then look at renewable energy generation.
I would focus on these "lean" items if not already done:
- Loft insulation
- Draught sealing (windows, doors, joints)
- lagging pipework and hot water tank
- If feasible but probably not: cavity or internal wall insulation, double or secondary internal glazing
Then, can the LPG boiler be replaced with a wood-chip or log fired unit, if you have a reliable fuel source? If you already have the "wet" system i.e. radiators in place, this could be a good bet.
Are the solar panels "PV" (i.e electricity generating) or the hot water type? You may find that the hot water type give you a better return against burning LPG than the PV ones will against electricity. A few sums should give you the answer.
The water-wheel sounds interesting... if you were a tinkerer, you could consider a DIY water heating system using for example an old car alternator, a 12V heating element and a thermostat. I take no resposibility for the results! The problem with a full-blown "micro hydro" system is the expense of generating 240V, 50hz electricity to feed your house in sync with the grid.
Let us know how you get on.
Olly :wave:
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Thanks Womble / Olly for those comprehensive answers. I think one incorporating a heat pump would be good - we can use the windmill we have for helping (a bit) with that. The waterwheel we have is only a 9m dia one and its unlikely to give us more than lighting (a 15m one would work better) but it's listed and we may as well use it for the mill itself (which is a self catering holiday let). I think that we may go for water heating with panels rather than selling to the grid etc, fortunately although the house is old it's not listed which should help. We're also going to get our non-insulated walls (thick stone) lined with a product from Kingspan (although OH has just discovered one by Cellotex which is cheaper) and the u-values it gives are impressive. Will let you know how we get on, house is being ripped apart starting next week so will be making our minds up on all of this soon as. Thanks again.
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And are you hoping you are back in for the winter?
I would be interested in how you go about the solar water heating panels. I am just starting to research that one - do you think it would need PP ? (We have a 5 year old house, so not listed or anything like that).
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we have a heat recovery ventilation system but we have a very airtight house. I knew someone who put one into a standard new build and wasn't worth it. frankly I wouldn't bother unless you are building an airtight house from scatch, in which case it is essential.
James
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Look carefully at the sums before discounting PV over solar thermal (water heating) panels.
The PV feed in tariff means you'll get back up to three times your capital over the contract for PV, as well as the electricity generated. We invested £15k in a 4kW PV array, and expect to earn around £40k income, plus the electricity over the 25 year contract (currently paying ~43p per kWh).
The solar thermal tariff (Renewable Heat Incentive) will give a much lower financial return (8.5p per kWh).
We couple it with a ground source heat pump, but our house (Victorian) was stripped back to bare stone and insulated to the nines, with underfloor heating downstairs and radiators upstairs. We've also got a wood burner in the lounge for quick bursts of winter heat.
So far it's all worked well, but as said above insulation is absolutely key.
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Hi Anke, don't think you will need pp for that one, but best phone the council to double check - my OH's parents live in a bungalow in Melrose and didn't need it but you will need building warrant which deals with the structure/weight ratios on your roof (you should be fine if its only 5yrs old) but it depends on how many panels you put up. We should be back in fairly quickly as the insulation part should be completed quite fast (some of it while we're still in) and the other fancy solutions can go in for the most part while we are still living here. Once we've decided and installed you'd be welcome to come up and have a look. It's quite interesting to see these things in the flesh - takes the techno out of it a bit.
Dan, many thanks, there's quite an initial outlay for panels and ground/air pumps which is the crunch for most people but of course we will have to consider if that is worth investing in long term. Feeling is at the moment that we would just like to reduce the imminent onslaught of winter bills considering the last 2 winters, although I must say once you start getting the buzz for saving and keeping reasonably cosy it becomes addictive and we don't want to be short sighted about it all. May be that we do it in stages starting with the obvious first (insulating and better usage of what we've got).
Thanks all, much appreciated. There'll be a lot more cups of tea over this one before a decision is made!
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Absolutely right, but if you've got the capital and plan to stay where you are for a while it's the best investment there is at the moment, a bit better than the 3% you'll get from the banks. :-\
Good luck with whatever you decide.
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ground source heat pumps work better with new builds as do all the fancy bits and bobs
wood chip boilers £50000 for a full set up and you can get feed in tarrif with this as well but your chips are £120 per ton
and the charts i have seen woodchip is not that much cheaper than oil heating :farmer:
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£50k would buy a pretty big shiny woodchip setup! But maybe you have a big house :o :)
Woodchip great if you have your own source, not so good if you have to buy it in. Pellet even worse.
Dan's right on feed in tariffs - they give solar PV a potentially good return on investment if you have a good south/SW/SE facing roof in a sunny part of the world. But not as good as (for example) loft insulation. I know you are all clever people and have done that anyway, but the principle bears repeating. Get the basics right first :)
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Yup, basics first. The plan is leaning towards sealing it, stuffing it, a solar panel for hot water, perhaps a heat recovery system, get the water wheel connected (is in brilliant nic and is perfectly do-able) and the windmill erected at the top of our quarry which between them should give us something.
Oh and investments in fleece pyjamas (attractive) may also be on the list. :D
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Sounds great! Please keep us updated with pictures as you go along, especially the waterwheel!
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Yes I will Olly, for anyone interested in industry, there's no nicer a thing than a waterwheel - we can turn it with one finger. The man who is coming to de-silt our mill pond has made his own wheel out of steel drums and gas cylinders cut in half for the buckets - it works brilliantly - I love these tinkering types! Must ask him to email me pics of that one too.
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Yup, basics first. The plan is leaning towards sealing it, stuffing it, a solar panel for hot water, perhaps a heat recovery system, get the water wheel connected (is in brilliant nic and is perfectly do-able) and the windmill erected at the top of our quarry which between them should give us something.
Oh and investments in fleece pyjamas (attractive) may also be on the list. :D
:D :D
I think the hot water bottle is very underrated; often it's all I need, tucked behind me in my chair, when the alternative would be lighting the fire or turning on the central heating.
And of course a good selection of thermal undies, good thick woolly socks and jumpers, fingerless gloves, heat-retaining hats...
We are always a little taken aback when we go into offices, where all the occupants seem to be in thin cotton shirt sleeves all year round. I know you have to keep workers warm enough that their fingers can operate the keyboard, but there is a bit of a distance between that and sultry... Years ago I had my own company, and kept finding that the employees had turned up the gas. I offered them all company cardigans - they got the message :D The office was in a converted granary loft, all listed and planning constraints - it had been a nightmare to get converted. There were skylights which meant that in summer the sun shone through onto computer screens. We'd have had to fit conservation-approved blinds at an insane amount of money each, so instead we bought them all sun visors (I think they were £2.50 each) - you'd see them get put on and taken off in a kind of Mexican wave around the office as the sun moved across the sky... :D
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;D ;D ;D great story Sally, I've seen me sitting at the laptop with tartan blanket round my legs, multiple jumpers, gilet, gloves and wooly hat and sun visor (can't shut out the limited day light there is in winter) all at the same time, thinking if only my clients could see me now. I must admit though I am completely in love with my electric blanket in the colder weather - I know I know, but it's my one luxury now that arthritis is worming its way around my joints. Salopettes (spelling?) are my norm in the cold days too - once they're on you don't want to take them off! Now where's that balaclava and snorkle parka....
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Hi , perhaps a bit late for the work you are doing but i thought i could perhaps help.
As other parties have correctly identified the most appropriate buildings for heat recovery systems are those that are air tight. Others have also mentioned that they want to retrofit internal insulation. These two topics are linked quite closely.
The risk of internal insulation in older buildings is one of damp endangering the fabric of the structure but also the health of the occupants through mould spores etc. (ie sick-building syndrome) :P
A well designed mechanical ventilation and heat recovery (MVHR) should allow the safe installation of modern cost effective insulation materials.
Only once you have done this should you consider the heat pump. Heat pumps have a lower flow temperature so can only be used with heat delivery systems that designed for that purpose ie underfloor heating or low surface temperature radiators. Heat pumps are fantastically efficient in efficient buildings, in inefficient buildings there is a very real risk of increasing energy consumption and costs.
Depending on how far you take all of this the next obvious addition would be electricity generation through PV, wind, or hydro.
I know it starts to look like a very serious shopping list. What you could end up with is a financially and environmentally sustainable home that not only protects you from rising energy costs but also provides an income through the Feed In Tariff or Renewable Heat Incentive (RHI) when it starts for domestic properties in 2012. Better still, team up with a neighbour to jointly heat 2 or more properties to access the lucrative commercial RHI. 8)
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I came accross a very interesting website with more info on this product: http://www.archiexpo.com/architecture-design-manufacturer/heat-recovery-unit-1245.html (http://www.archiexpo.com/architecture-design-manufacturer/heat-recovery-unit-1245.html)