Thu, 21 May 2026 21:36:00 +0100 https://www.greenbuildingforum.co.uk/newforum/ Lussumo Vanilla 1.0.3 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=51727#Comment_51727 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=51727#Comment_51727 Sat, 11 Apr 2009 12:05:48 +0100 a_russell https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=51729#Comment_51729 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=51729#Comment_51729 Sat, 11 Apr 2009 15:01:01 +0100 SteamyTea Solar gain is of very little use on its own and can only really be considered in conjunction with the properties of the building i.e. the heat losses, design, thermal mass.

To give you an idea down here in West Cornwall we receive 1200kWh at an average of 135 W/m². This is enough to heat a well insulated house of high thermal mass (assuming the mass is within the insulated envelope).
If you wish to work out how your house is affected by solar heating first you need to establish the heat losses of your dwelling, what the expected difference in temperatures are, how you will 'collect and store' the solar radiation etc. The only rule of thumb that I could think up would be to collect much more than you need and increase air changes to get rid of excess heat. Oddly enough it is overheating of dwellings that cause the major problem for designers but this is partly because we don't incorporate solar gain and thermal mass into the design process yet.

Not much help I am affraid.

Nick]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=51736#Comment_51736 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=51736#Comment_51736 Sat, 11 Apr 2009 17:21:15 +0100 biffvernon
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Be interesting to see what that blanket looks like :)

Nick]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=52982#Comment_52982 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=52982#Comment_52982 Wed, 29 Apr 2009 18:04:27 +0100 DaveOxford
Not sure about your figures. Irradiance at this latitude will be around 1 kW/m2 when the sun is out, perhaps a bit more. I don't understand your second figure. Is it KWh divided by hours in a day to give an average figure?

Anyway, it's a lot of power, a_russell, and if you have a south-facing window, you can count on gains in proportion to your window area.

What happens to that energy after it enters your building depends on the usual suspects - thermal mass, air-tightness, insulation etc. etc., as Nick says.

There are interesting trade-offs to consider: In all buildings, there is a tension between increasing window size to admit daylight, and decreasing window size to reduce heat loss (or, sometimes, to limit solar gain). Approved Document L1A of the Building Regulations (Office of the Deputy Prime Minister, 2006), which is concerned primarily with energy conservation, recognizes these conflicts:

‘When seeking to limit solar gains, consideration should be given to the provision of adequate levels of daylight. BS8296 Part 2 Code of practice for daylighting gives guidance on maintaining adequate levels of daylighting. The Building Regulations do not specify minimum daylight requirements. However, reducing window areas produces conflicting impacts on the predicted CO2 emissions: reduced solar gain but increased use of electric lighting.’

So be aware that, unless you have sufficient thermal mass to absorb solar gain and so moderate internal temperatures, you CAN have too much of a good thing.

Dave]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=52991#Comment_52991 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=52991#Comment_52991 Wed, 29 Apr 2009 20:19:24 +0100 trule
A rough calc for the m2 might be: (Wloss rate house * 24) / Gvalue window / Wsun m2 / Sun hours

eg, spring time 500 watts heating loss, 5 hours sun 500 watts sunlight : 500 * 24 / .6 / 500 / 5 = 8m2

its more complex than that but you get the idea.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=52992#Comment_52992 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=52992#Comment_52992 Wed, 29 Apr 2009 20:23:27 +0100 tony
I prefer to store the gain for use later by employing high thermal mass, this allows maximum use of the gain and is a more comfortable way to live.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53006#Comment_53006 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53006#Comment_53006 Wed, 29 Apr 2009 22:08:40 +0100 SteamyTea
Top of my head I think it was the RMS value (kW) divided by the yearly hours (8760), this was research about thermal mass and solar gain and not purely about solar power. Was 2 years ago I did the research though so would have to go back and dig out the paper to find out for certain. Down here in Cornwall we tend to get a bit more sunshine that most places in the UK and when it does shine it is of higher intensity (cause we are South).

I intend to build a solar heated dwelling as part of my MSc so I have somewhere to collect real data, but I need to find some funding fast for that, but shall publish the results when I have finished no doubt. Will be interesting work as I shall be looking at it from a statistical view point rather than the pure physics for a change.

Nick]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53010#Comment_53010 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53010#Comment_53010 Wed, 29 Apr 2009 22:13:29 +0100 tony https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53014#Comment_53014 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53014#Comment_53014 Wed, 29 Apr 2009 22:49:38 +0100 SteamyTea
As I am sure you can imagine it does not shine at a constant rate, this affects the amount of energy absorbed by a mass, so but looking at the probability (similar to a windspeed probability) of a certain amount of insolance striking the body one can calculate ideal properties i.e. response times for a dwelling to maximise thermal gain without overheating.]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53017#Comment_53017 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53017#Comment_53017 Wed, 29 Apr 2009 23:29:15 +0100 tony thanks]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53021#Comment_53021 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53021#Comment_53021 Thu, 30 Apr 2009 01:31:56 +0100 DaveOxford
The only place I know that is heated entirely through solar gain (plus the inevitable casual gains) is the Berm House at Caer Llan. They might consider letting you put some instrumentation in there. Interested?

Dave]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53025#Comment_53025 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53025#Comment_53025 Thu, 30 Apr 2009 08:05:34 +0100 SteamyTea
Thanks for that. There is a place down here at St Issy that was designed purely as a solar house that I have used data from. What I am trying to mimic is an ordinary terraced house, may be just cheaper to use mine but may get the university to find some cash so that I can build a model. Trouble is models are not that accurate as they don't allow for normal usage.

Nick]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53078#Comment_53078 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53078#Comment_53078 Thu, 30 Apr 2009 17:14:06 +0100 DaveOxford
I thought you meant you were having to build a full-sized bumper jumbo family sized real house in order to get your data, and that you might get funding for that (respec!). Just a model, then? Are we talking test-cell? Have you considered simulation with something like IES? - no messy glue or building, just a computer. Student license is £50, but learning to use it will drive you bonkers. Whcih course?

Dave]]> https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53084#Comment_53084 https://www.greenbuildingforum.co.uk/newforum/comments.php?DiscussionID=3862&Focus=53084#Comment_53084 Thu, 30 Apr 2009 18:44:51 +0100 SteamyTea
Looking into the MSc in Sustainability and Risk Management, but not totally made up my mind at the moment, got to make my mind up soon though.

Model will be about 1/3 scale, large shed size, should be large enough to get some idea or real life situations. Last years dissertation was modeling solar gain, response times and the effects of thermal mass on storage and it soon became apparent that what is needed is real primary data. My lab model and the computer model matched well, but conditions within a lab are way too stable really. So unless anyone knows of anyone that is looking to do research work with deep pockets, I am going to have to fork out myself :(

Nick]]>