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Green Building Bible, Fourth Edition
Green Building Bible, fourth edition (both books)
These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment.

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    • CommentAuthorBruce Davis
    • CommentTimeOct 17th 2008 edited
    Hello Green Homeowners, My name is Bruce Davis and I live in Vermont in New England where I have built a house with my wife using our own labor. We live in the a heavily forested region that was mostly open pasture land for sheep and cows in the 19th. and 20th. centuries.We have built our house using the principle of local materials(stone,wood) and we heat with wood ( wood boiler) from our own forest.The reason I am writing this note is to start a discussion on the subject of insulating shutters for windows that I haven't yet seen on your site.The point being is that to date most houses have been brought up to a certain standard of insulation value people may be wondering where more gains in heat conservation might be made owing to the recent steep increases in fuel costs.As we have much the same heating issues here in America even with a plentiful supply of wood,I have concluded after some reflection that the greatest heat loss is now taking place through the windows.
    • CommentAuthorarthur
    • CommentTimeOct 18th 2008
    I'm also surprised that insulated shutters aren't more used or talked about. They seem the obvious answer to the problem of utilising daytime light and solar heat but mitigating the downside of nightime heat losses. Also useful for keeping buildings cool in summer.
    • CommentAuthorhoffman
    • CommentTimeOct 18th 2008
    I found windows are indeed a major source of heat loss in my new build calculations. Also thought about making some sort of insulated shutter with maybe a plywood / insulation sandwich. The U value when the shutter is closed during the night and maybe in the day if the room is unused is magnitudes better.

    Bruce, your shutters are external which would be quite rare in the UK, internal shutters being more common usually on older properties. External would be more common in mainland Europe. Do you think your plans be adapted for internal shutter? (non louvered). This would be of great interest from me and possibly others on the forum.
    • CommentAuthorfuncrusher
    • CommentTimeOct 19th 2008
    The topic has long been raised on the forum by several people including the ususal suspects. It is actually become more relevant for two reasons. Firstly, all enhancement of insulation produces diminishing returns, and in the case of walls and ceilings losses are easily reduced to minimal levels. That leaves windows, even with DG, as the major escape route for heat. Secondly, higher building regs on overall thermal losses are forcing people to greatly reduce window sizes to meet the limits imposed. The resulting 'houses' are not quite caves, but certainly heading towards dark medieval houses (where cost of glass was the motivation for small windows), with greater lighting requirements all year - ignored by regulators! My understanding also is that calculations make no allowance for use of either shutters or curtains: typical crazy government.

    Those who have looked at the problem, including myself, have not come up with a good design. There are 3 challenges: tightness of fit, insulation property, and concealment when open. Reasonably tight-fitting traditional internal wood shutters do quite a good job, as wood is quite a good insulator, and they fold back into shutter boxes to form an attractive feature when not in use. The fact that overnight even DG gets mass condensation behind the closed shutters proves the point. With heavy curtains added, the effect must be substantial.

    Obviously this is only a saving at night, but at UK latitudes and climate that is a very substantial factor, albeit it requires a commitment by occupiers to open and close each day.

    External shutters are theoretically desirable, but I see little likelihood of people shutting them nightly. There are also obvious aesthetic and practical problems. Concealed and automated external 'security type' insulated roller shutters could be incorporated in new-build at a price.
    Something I've found out about recently are "cellular shades". These seem to be popular in the USA. They fold up (or down) neatly and expand out to trap air.

    This one has side tracks and so should give a good seal:


    They are claiming a US R value of 4.6 (= 0.81 m^2K/W). This is pretty significant if true as it's better than most new double glazing! But it also says that's for "double pane", so maybe they mean that's the cumulative value with some "typical" double glazed window behind it, in which case it's not really that impressive. (Or do you get more resistance if the temperature difference across the component is lower because of better glazing? This is physically concievable; I will ask them.)

    The exterior security roller shutter thing would be another option. I know these are a mass market product in Germany, but I don't know whether they have a significant insulating effect.
    • CommentAuthorGotanewlife
    • CommentTimeOct 19th 2008 edited
    So, as it happens I DO have loads of external lovered shutters covering both doors and windows on 2 floors (with wraparound balconies), and even if shutting them might be a bind for us I am sure we could add it to my 10 year old's Pocket money agreement:wink:. So, have just paid for the info and I'll let everyone know what I think. A bit skeptical because there are no photos or descriptuions of what the finished item looks like and since I now live in Italy (where form follows exactly the way it has always been or it is "Brute!' (ugly)) I woonder if I have just wasted 3pounds50.

    Meanwhile, given I will insulate my roof, draught proof all my doors and windows and leave my solid stone walls alone for now (oh and the "up to 40% savings" claim), is it better to insulate the shutters or double glaze the windows ('better' as in measured strictly by fuel savings fo heating)?
    • CommentAuthordickster
    • CommentTimeOct 20th 2008
    Our proposed new build has 400mm deep walls, allowing internal insulated shutters (yet to be sourced/made at home) on all windows.

    Should increase insulation by "quite a lot" (technical term). I fancy, as mentioned above, a lightweight sandwich of ply and polystyrene?
    • CommentAuthorjoe.e
    • CommentTimeOct 20th 2008 edited
    That sounds ideal. Maybe with rubber seals around the edges of some suitable profile, so that they are relatively well sealed when closed - http://www.tym.co.uk/ do lots but there are plenty of other suppliers.
    Turns out that is the cumulative value of the cellular shades plus the window.

    So the contribution in US units is about 2.7 i.e. 0.47 in metric or a metric U value of 2.1.

    Thats still not bad; almost as good as a typical modern window itself. So in the winter if you used them 2/3 of the time (i.e. when it's dark), you might save about 1/3 of window heat losses overall. And most people have some sort of blinds anyway.

    The person I emailed said that with sidetracks you got an extra 1, giving 3.7, although they didn't really justify this. They also said they were going to get more figures from the manufacturer of the material, hopefully soon.
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