Mon, 25 May 2026 18:19:06 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=16864#Comment_16864 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=16864#Comment_16864 Sat, 22 Mar 2008 11:14:06 +0000 James Norton
...So I design to passiv-haus standards, including airtightness insulation, MHRV I have some evac tubes on the roof with , even a little PV but is there any way I can get a family's worth of hot water during the winter without mains gas backup (or oil or LPG)...?

..thoughts so far...

Woodchip boiler - costs? pollution? wood supply / store?
Electricity - heatpump? but still based ultimately of fossil based mains generation(!)
Huge heat store with lots of Evac tubes - cost? reliability?
Woodstove w/ back boiler - pollution? excess room heat? airtightness?

J]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17227#Comment_17227 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17227#Comment_17227 Wed, 26 Mar 2008 09:04:12 +0000 James Norton
This seems to me to be a pretty big question....

Your gas creates C02 and will run out...
PV doesn't well enough in cloudy winter... same for Evac Tubes...
Wind turbines can't beat the planners or low urban wind speeds...


So what ya gonna do....?


(Cold showers may work for Biff and Tony but not for my misses I can guarantee that!)

J

]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17238#Comment_17238 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17238#Comment_17238 Wed, 26 Mar 2008 12:08:01 +0000 stephendv 1. CHP generator (veggie oil). Since my elec is being met by PV, if there's no sun for leccie, then there's no sun for hot water either. So turning on the generator to create both hot water and elec makes sense.
2. Log burner with back boiler. House is rural so a fireplace is essential :) might as well make good use of the heat.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17249#Comment_17249 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17249#Comment_17249 Wed, 26 Mar 2008 16:16:55 +0000 Chris Wardle
Likewise with the space heating. Design to the highest standards of insulation and air tightness and stick a cheap wall spilt ASHP in your main living room for £799. What's the point of spending any more on systems that will hardly ever be used? Just a waste of resources.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17265#Comment_17265 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17265#Comment_17265 Wed, 26 Mar 2008 18:53:02 +0000 sune
What about a gasification boiler like a vigas boiler combined with a large thermal store that stratifies well. The good thing about these is you can burn just about anything - they do cost a fair bit though.
You might consider a wood stove linked to a good thermal store. It would be cheaper than the gasification boiler anyway.

What about some sort of heatpump (either a ground one or an air one) which dumps into a thermal store....quite pricey though...you could have you own windmill to power it or sign up with someone like good energy for your leccy....]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17268#Comment_17268 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17268#Comment_17268 Wed, 26 Mar 2008 19:21:22 +0000 llwynbedw Posted By: James NortonOk...
...So I design to passiv-haus standards, including airtightness insulation, MHRV I have some evac tubes on the roof with , even a little PV but is there any way I can get a family's worth of hot water during the winter without mains gas backup (or oil or LPG)...?

I am scratching my head over the same issue for a house in west Wales. GSHP and underfloor heating sounds great but there's no way my wife is going to accept tepid water in the winter time or probably any other time. For DHW I think 60C is overkill, but even a modest 48C is quite a step up from the 35-40C I assume you can expect to get from a GSHP. I'm leaning towards a log boiler and a large thermal store that supplies both the domestic hot water and hot water for the UFH. Add solar water heating and you probably could get by with very little wood over the summer months. But then there's the electricity for the UFH pump to consider and maybe for the log boiler as well...

Chris Wardle commented: "Design to the highest standards of insulation and air tightness and stick a cheap wall spilt ASHP in your main living room for £799. What's the point of spending any more on systems that will hardly ever be used? Just a waste of resources."

Totally agree about insulation and draught-proofing. The problem with the ASHP approach is that each room you're actively using will need an ASHP. I live mostly in Japan, where central heating is not used. The result is that the house ends up festooned with external ducts and boxy fan units for multiple aircon/heaters (one in each room) which is ugly in the extreme and gets expensive quickly. The alternative is to have only one of these devices and never use the other rooms in the winter because it's too cold, or heat them with inefficient fan blowers. I've experienced houses without central heating and to me it's not the answer. Personally I would prefer to pay for the comfort and security of a central heating system and use it sparingly than save the money and struggle to keep the house warm during an unexpectedly chilly winter. I do accept that notions of "cold" vary from person to person and we all have our own ideas on how much should be spent.

Dan]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17273#Comment_17273 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17273#Comment_17273 Wed, 26 Mar 2008 20:06:43 +0000 Cds
There is a reason for storing hot water at 60ºC, Legionella Bacteria.

Legionella Bacteria can survive low temperatures and thrive at temperatures between 20°C- 45°C. At 60ºC the bacteria can not survive.

My understanding is that most GSHP will have some form of direct back up such as a heating element to meet hot water demands.

Richard]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17323#Comment_17323 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17323#Comment_17323 Thu, 27 Mar 2008 15:14:09 +0000 Chris Wardle
As soon as you start plumbing heat distribution systems and boilers in that saving is lost and they just cost more to build. You end up paying a lot of money for piece of kit you only actually need for a few weeks a year. Just seems like a waste of money to me.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17326#Comment_17326 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17326#Comment_17326 Thu, 27 Mar 2008 17:14:41 +0000 llwynbedw Posted By: Chris WardleDan, are the houses in Japan designed to PassivHaus standards? I doubt it so certainly a central heating system is required. The idea behind PH is that you design out the need for central heating by spending more on getting the insulation and airtightness etc right and off-set that additional cost against the savings from not installing a conventional heating system.
As soon as you start plumbing heat distribution systems and boilers in that saving is lost and they just cost more to build. You end up paying a lot of money for piece of kit you only actually need for a few weeks a year. Just seems like a waste of money to me.
Housing in Japan seems to be pretty poor to me. Although in Hokkaido there are homebuilders that do actually talk about thermal bridging and how to prevent it I have also seen housing of very poor quality despite the cold climate up there. Around the Tokyo and Osaka regions where it is significantly warmer in the winter nobody seems to talk about insulation or energy usage. The private homes and condos I have visited generally seem to have a poor combination of low thermal mass, inadequate insulation and draughts! (Modern condos built within 10 years excluded.) I think part of it is the cultural attitude that a house cannot or should not last more than 30 years - why bother throwing lots of money at it? Just my theory.

I appreciate the thinking behind the PassivHaus concept, I'm just not convinced that it will feel "right" temperature-wise to live in without more than one heat source. It seems to me to be an extreme solution with no margin for error. A case of belt and braces perhaps...

Dan]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17330#Comment_17330 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17330#Comment_17330 Thu, 27 Mar 2008 18:19:59 +0000 jon
Unfortunately there are also other less common pathogens that can survive to 114C or so. Ideally any system routing water might take the temperature up to perhaps 130C before storage.

There are possible new technologies that could solve the dilemma. However any new technology that might be visible to the public (almost all new renewable technology) will not have been planned for by the planners and so will have difficulty being introduced into this country until proven elsewhere with the UK planning laws subsequently re-written to account for it.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17332#Comment_17332 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17332#Comment_17332 Thu, 27 Mar 2008 18:39:30 +0000 tony

Joke? it will all be steam!!! not water!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17334#Comment_17334 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17334#Comment_17334 Thu, 27 Mar 2008 18:43:22 +0000 Cds
Interesting, domestic indirect systems could only ever get up to about 80ºC and the norm is around 60ºC. Are we all at risk from these other pathogens?

Health and Safety legislation tends to concentrate on Legionella although systems should be flushed and possibly disinfected before use.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17338#Comment_17338 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17338#Comment_17338 Thu, 27 Mar 2008 19:23:33 +0000 jon https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17339#Comment_17339 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17339#Comment_17339 Thu, 27 Mar 2008 19:26:06 +0000 Cds
Well as I have got to nearly 50 I’m not going to start worrying now!]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17340#Comment_17340 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17340#Comment_17340 Thu, 27 Mar 2008 19:32:36 +0000 James Norton
So back to topic then...

Can you get a small biofuel CHP?, application envisaged in the thread would be 2 households min, but maybe 5 or more?

http://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1458&page=1#Item_11

Also just how big an array / accumulator would you need to get a big input into winter DHW from Evac tubes...?


J]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17371#Comment_17371 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17371#Comment_17371 Fri, 28 Mar 2008 09:36:38 +0000 jon
I haven't been able to get any real data on how many evac tubes would be required. Will be very interested if you find any data.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17374#Comment_17374 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17374#Comment_17374 Fri, 28 Mar 2008 10:28:25 +0000 fostertom Posted By: jonways to obtain very hot water (100C+) from stationary arrays by considering the house or structure itself as a solar collectorHow's that, Jon?]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17378#Comment_17378 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17378#Comment_17378 Fri, 28 Mar 2008 10:56:06 +0000 jon
There are various solar mirror reflection arrangements that allow fixed concentration with one or more moveable receptor(s): This allows medium to high grade energy production but you almost certainly wouldn't use it to its full potential in residential use. You would just need to design the roof or the facade as one of these reflector types adding a cost of about £30 a sq m assuming mass production together with the receptor apparatus (the larger cost): Means that the house shape and layout with regard to solar movement is partly dictated by the type of reflection gathering system you choose (which is why it is currently infeasible in the UK: Our planning system is not geared up to use innovative renewable energy)]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17382#Comment_17382 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=17382#Comment_17382 Fri, 28 Mar 2008 11:24:51 +0000 Ed Davies https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=18061#Comment_18061 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=18061#Comment_18061 Sun, 06 Apr 2008 23:06:34 +0100 Noyers Live in France and heat domestic hot water by electricity, cheap rate. EDF (Electricity de France) generates electricity as follows: -

Nuclear 87.5%
Renewables 5.9%
Coal 3.3%
Gas3.2%
Oil 1.6%
Other 0.3%

Look no oil! (Well all right 1.6%).
Of course the downside is that fission nuclear reactors can hardly be described as "green" and everyone here lives too near to one.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=21359#Comment_21359 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=21359#Comment_21359 Wed, 21 May 2008 18:57:19 +0100 mrswhitecat https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=21361#Comment_21361 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=21361#Comment_21361 Wed, 21 May 2008 19:14:34 +0100 joe.e Posted By: jonDidn't say it would be easy Tony, just ideal: You can also get away with 115C but this tends to be a less economic way of doing it. Steam only gets produced at 100C as a forced change of state, given sufficient energy input, at standard atmospheric pressure. I don't think we are at serious risk from pathogens that can survive at greater than 60C Cds but it's not my area of expertise.
According to my father (retired anatomy lecturer), 120C for 20mins is the rule of thumb. That leaves water sterile for all practical purposes - only real exotics can survive that. But we've all been getting by with hot water that's a lot less hot that that (obviously), and bathwater-related deaths seem mercifully rare.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=21384#Comment_21384 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=21384#Comment_21384 Wed, 21 May 2008 20:31:53 +0100 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=21422#Comment_21422 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=21422#Comment_21422 Thu, 22 May 2008 07:14:08 +0100 spynappels https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=21424#Comment_21424 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=21424#Comment_21424 Thu, 22 May 2008 07:16:05 +0100 spynappels https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=22637#Comment_22637 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=22637#Comment_22637 Mon, 02 Jun 2008 22:44:00 +0100 Noyers Will a house to passivehaus standards + MHRV need any heating over and above the wood burner with back boiler you need for spring/summer weather such as we now have in SW France (where it's rained most days since March). Any solar system would need to be pretty efficient to make much impact this year!

"spynappels" - Have there ever been deaths from Legionella of fit people living in private homes? The risks must be minute. I'd be more worried about drunk drivers, lightening strikes.....]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=22734#Comment_22734 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=22734#Comment_22734 Tue, 03 Jun 2008 22:16:59 +0100 spynappels Posted By: Noyers
"spynappels" - Have there ever been deaths from Legionella of fit people living in private homes? The risks must be minute. I'd be more worried about drunk drivers, lightening strikes.....

True, but that might have to do with the fact that the building regs now demand water stored at temperature must be heated to above 65 degC periodically to kill all the bugs. An instantaneous type water heater does away with this requirement.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=22843#Comment_22843 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=22843#Comment_22843 Wed, 04 Jun 2008 18:31:36 +0100 Pete1951 I too am building a PassivHaus/CSH level 6 house and I posted a very similar question on the UK PassivHaus Forum. If there is to be no conventional central heating and if mains gas isn't available, as in my case, the replies split into two camps. The first one thinking a simple low cost immersion was best, the other was to use an ASHP and reduce CO2 production. I have decided to use the simple option. To get around the Legionella problem I will be using a 300l heat store with an external heat exchanger giving me mains pressure hot water. I hope that helps.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=22975#Comment_22975 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=22975#Comment_22975 Thu, 05 Jun 2008 23:50:27 +0100 Rhisenburger Hi,I moved to the UK about 2 years ago from the states. Before I left I just started hearing about tankless hot water. Basically, the hot water is heated as you use it. Here is a link for it : http://www.gotankless.com/. These in particular are electric, but are also available in a propane or oil. They will definitely provide the plenty of hot water, some companies won't install them without plastering warning stickers on each faucet in the house. I did notice in a few houses over here something similar in the showers, but the ones I speak of are for the whole house. Obviously, this will add to the cost of running the house; but I believe if you want the misses happy it's the way to go. Not to mention you can roast those bugs everyone seems so worried about.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=28154#Comment_28154 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=1453&Focus=28154#Comment_28154 Thu, 24 Jul 2008 23:21:34 +0100 Noyers MHRV from Rega Ventilation, 21 Eldon Way, Biggleswade, Beds SG18 8NH - not installed yet but have heard fans running at factory and doubt you'll be able to hear them at all once installed.]]>