modern houses , both energy efficient and conventional, pride themselves on full height glazing . wondering what others think about this .
good or bad ?
ecofriendly or not?
how much glass is too much ?
(23 posts) (8 voices)-
Posted Tuesday 8 Feb 2011 @ 9:49:52 pm from IP #
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Dave, thanks for leading the thread.
To my mind, nothing shows the hypocrisy, self deception and frivolity of people claiming to support sustainable living so clearly as the enormous windows of their houses.
You will note that I am trying to moderate my language. I appreciate that the dictates of fashion may trump any other considerations. Housing design magazines have a lot to answer for in encouraging stupidity and waste.
Posted Tuesday 8 Feb 2011 @ 11:19:25 pm from IP # -
SteveJ
MemberCatopsilia said - "To my mind, nothing shows the hypocrisy, self deception and frivolity of people claiming to support sustainable living so clearly as the enormous windows of their houses."
I feel that is a very simplistic and narrow viewpoint. Granted most designs featuring glass walls fail from an “ecofriendly” perspective but not all designs are equal. I think if one was to generalise it could be said that without a holistic design approach it seldom works well but by applying good design it is an invaluable way to create a sustainable building.
I should declare my interest straight up as I have one of 'those houses' with 4 meters of glass across the 32 meters front that make up the house. In the context of my building such glazing is a very good thing, our house is 100% autonomous and suites the climate perfectly. The glazing system allows the building to completely and passively heat and cool itself. It is considered a sustainable house not only in its high functionality but also due to its low embodied energy construction and built in deconstruction potential. I believe that high visual amenity is also very important in building design, functional glass walls add greatly to this.
As for Good or Bad? It depends where the glass is, what type of glass is used, where the glass comes from (salvaged in the case of my house) whether or not the glass is considered in a larger passive solar design with appropriate eave design and cross flow potential, impacts on other energy use such as lighting requirements etc. There are a whole bunch of factors that impact on "Good or Bad" "ecofriendly or not".
Steve
Posted Wednesday 9 Feb 2011 @ 12:34:01 am from IP # -
I dream to have a home build from the glass sheets completely.
Walls build of two or three glass layers with sealed space between.
On demand you could pump colorful fluids between to change color of your house or room depending on your mood of fashion.
To transfer heat in or off.
Insert inertial gases between for perfect insulation.
Save money on windows, and blinds.
Look at stars at night through glass ceiling.
Instead on vacuum cleaner you could use water blaster to clean the dust or sprinklers - with slight sloping floor could be easy self cleaning automate.
We can use the most abundant resource on our planet - sand -as building material that is also 100% recyclable.
No fire risk.
Glass well made is as strong as a steel.
Clean , no place for germs to hide, termite to bite, mouse to crouch.Use nano-micro-fluid containing tiny solar cell, + battery capacitor - floating between wall like human blood cells to collect sun energy and feed the energy for home.
What can I say more about house from glass?
Posted Wednesday 9 Feb 2011 @ 12:53:00 am from IP # -
Buzzman
MemberYes but given that around 40% of heat gain/loss is via the windows, the less glass area the better.
Unless, of course, it is all double or triple glazing, or is shuttered or curtained or otherwise prevented from making/losing all that energy.
And as glass has a lot of embodied energy incurred in it's manufacture (and doubly so if encased in aluminium or PVC frames) the same rule applies - less is best.
Under the BCA the requirement for natural lighting in any given room or space is, IIRC, not less than 8% of the floor area in habitable rooms. More than 10% therefore could be said to be excessive.
Some academics have argued that, for hot, dry climates, the maximum should be even less, around 1/16th of the floor area.
Posted Wednesday 9 Feb 2011 @ 1:22:52 am from IP # -
A bit like this one, Greenozi?
http://architecture.about.com/od/greatbuildings/ig/Modern-and-Postmodern-Houses/Glass-House.htmPosted Wednesday 9 Feb 2011 @ 1:29:11 am from IP # -
Catopsilia
You see concept is not new at all, I just want a bit more privacy so my walls are colorfull, and only semi transparent when where needed.
Next interesting aspect - when walls are transparent sun and heat radiation could go thought the wall, across the building ,without been all absorbed inside.Posted Wednesday 9 Feb 2011 @ 1:49:33 am from IP # -
Jeffbloggs
MemberGreenozi
Why not use fungi and anaerobic bacteria to fill the glass panels, they would then "grow" according to resources, feed and sunlight. A living wall so to speak. Make the walls out see thru CNT though. BTW CNT's only conduct heat/electricity down the length of the tube and not sideways across the tube, maybe use these like LCD displays to polarise/filter/insulate light/heat radiation?-
Personally, I think using common glass walls in a house is like having a radiation and insulation "hole" in the house. A 1m² window in the summer is also a 1kW radiative heater, plus some conductive/convective airflow loses from the pane, and up to 3x as much conducted through an aluminium frame as through the glass itself. A window left "open by mistake" can easily destroy any effort to maintain comfort in a home ie it really is a hole.
There are of course a range of window "treatments" to cover this hole. They range from roller-shutters to LCD blinds, but unless they are actually used correctly they have no impact on the hole, and are the equivalent of leaving the window "open".
Essentially there are only two states that a house is in to maintain comfort.
- The outside climate is comfortable and therefore the house is left "open"
- The outside climate is uncomfortable and therefore the house needs to be "closed" and "climatised"These states do not just fluctuate during the seasons, they can/should also be used for fluctuations during the day. For instance in winter you might want to let the heat in during the day, and in summer you want to let the heat out at night. They really need to be actively controlled for the best effect.
Now when I say "climatised" I mean by whatever means available, from AC to passive thermal mass heating etc. But when climatisation is required, the house really needs to be closed, it should not be able leak heat in or out of the house via any "holes". But there are however, two further requirements to make a house livable, that windows provide; One is lighting to the inside of the house, and the other is ventilation.
Lighting can be via skylights etc or well treated, efficiently sized DG windows (preferably with limited, but effective openings for ventilation when the house is "open"). If there are views the sizing will always be a compromise, with the views generally winning dominance. As with passive heating through glass, and security and property protection, the correct window treatments are essential to maintain efficient climatisation of the home. Insulated exterior protection is best. Without them the windows remain a "hole" for uncontrolled radiation, conduction and convection of heat into and out of the home. BTW for cross ventilation one need not only use glass windows, any insulated and opening wall panel can acheive this, the glass part is unessecary, but sadly the most common way of providing ventilation.
Ventilation on the other hand can be more readily be dealt with, via shared ducting with HVAC system, and by using a "real" HRV system heat exchanger(non-roof space version!) which can recover up to 90% of your energy loses/gains to the environment from ventilating the house. It will provide min 3x air volume replacement per hour from a small fan, to all rooms, without anyone needing to open a window for ventilation. The air quality and comfort are more controllably maintained, and it can operate continously, reducing the need for "uncontrolled" opening windows for ventilation altogether. A enthalpy wheel HRV can also be used for humidity control, further reducing the heating/cooling requirements of the home. A window cannot do this at all, it is after all, just a hole.
Posted Wednesday 9 Feb 2011 @ 2:07:55 am from IP # -
There is a famous story, Greenozi, of an owner being very disappointed by the difficulty of living in her glass house:
http://architecture.about.com/od/houses/a/farnsworth.htmThese houses were criticised in political terms:
"In April 1953, House Beautiful magazine responded with a scathing editorial which attacked the work of Mies van der Rohe, Walter Gropius, Le Corbusier, and other followers of the International Style. The style was described as a "Threat to the New America." The magazine insinuated that Communist ideals lurked behind the design of these "grim" and "barren" buildings."Posted Wednesday 9 Feb 2011 @ 2:15:21 am from IP # -
SteveJ
MemberBuzzman - 40% of heat gain/loss is via the windows
Where is this figure from?
The embodied energy of glass is not as bad as you may think considering its very long lifespan, it is easily reused and /or recycled.
MATERIAL PER EMBODIED ENERGY MJ/kg
Kiln dried sawn softwood 3.4
Kiln dried sawn hardwood 2.0
Air dried sawn hardwood 0.5
Hardboard 24.2
Particleboard 8.0
MDF 11.3
Plywood 10.4
Glue-laminated timber 11.0
Laminated veneer lumber 11.0
Plastics – general 90
PVC 80.0
Synthetic rubber 110.0
Acrylic paint 61.5
Stabilised earth 0.7
Imported dimension granite 13.9
Local dimension granite 5.9
Gypsum plaster 2.9
Plasterboard 4.4
Fibre cement 4.8*
Cement 5.6
Insitu Concrete 1.9
Precast steam-cured concrete 2.0
Precast tilt-up concrete 1.9
Clay bricks 2.5
Concrete blocks 1.5
AAC 3.6
Glass 12.7
Aluminium 170
Copper 100
Galvanised steel 38Source: Lawson Buildings, Materials, Energy and the Environment (1996);
* fibre cement figure updated from earlier version and endorsed by Dr. Lawson.Really these things should be looked at using the Gross Energy Requirement (GER) (true measure of embodied energy) but it is impractical to measure but places glass as a better material.
I would never consider using any thing but 2x or 3x glazed glass in H/W framing.
Steve
Posted Wednesday 9 Feb 2011 @ 5:09:57 am from IP # -
Jeffbloggs
MemberStevej
Are the figures you posted GER? Do you have a link to those otherwise?Posted Wednesday 9 Feb 2011 @ 5:26:22 am from IP # -
dymonite69
MemberGlazing serves multiple purposes - aesthetic, views, lighting, passive solar.
If you are a purist then you design in enough glass to achieve optimal thermal conditions - no less or no more. Clearly the amount is dependent on solar access, shading, insolation, climate conditions and thermal mass. You can't stipulate this in absolute amounts. But you may need to compromise to achieve the other goals.
But what is clear is that some solar glass can be good for heating but lots is not necessarily better (for energy efficiency). There is an optimal value (in maths/engineering/physics terms) that needs to be calculated for the site, orientation and design.
Posted Wednesday 9 Feb 2011 @ 6:30:25 am from IP # -
Buzzman
MemberSteveJ
The 40% figure is an estimate based on my own my own experience of modern housing design and the people who live in them.
When govts calculate the figures normally given (20-60%) they generally assume a "rational man" lives in the house.
Usually the 'man' is anything but rational and most prefer views to heat gain/loss, so the averaged figure takes this into account.
The percentage of heat loss (or heat gain) varies markedly according to latitude, continental location and elevation.
Even the windows industry gives higher figures for heat gain:
http://windows.build.com.au/s01/energy_efficient_windows/windows_energy_rating_schemeIt also varies according to internal and external window treatments. For example, whether or not you have external shutters, or heavy drapes with pelmets inside, or both for that matter.
For example, the percentage of heat loss in winter may be greater in Tasmania than North Queensland, whereas the percentage of heat gain in summer may be the other way round.
When talking to people about it I generally use 30% as a rule of thumb, because I am mostly talking to coastal people on the NSW mid-north Coast.
Interestingly, QLD, NSW and VIC govt sustainable house sites give conflicting figures for the improvement in this when using double-glazing over single glazing - from as little as 10% improvement up to 40% improvement.
So if 40% of 87% of heat is kept out by DG, this means 52% of the heat gain from windows is still getting in (according to my admittedly miserable maths).
So at best DG can only keep out 20% of total heat. (I think)
Whatever.
Glass is melted in massive furnaces using natural gas or oil fires. Most glass cannot be made from recycled glass, so has to be made from fresh raw material - high silica content sand.
Admittedly recycled glass does use less energy to make than new glass, but as it isn't separated anything like enough, recycled glass always contains clear, green and brown glass, so can only be used for the latter once recycled.
(Source ACI Glass - factory tour)External shade is considered MUCH better than internal window coverings, with pergolas and tree shade rating far better than DG.
http://www.sustainability.vic.gov.au/resources/documents/Window_protection.pdf
Interestingly, another publication out of VIC says this DG be as much as 40% better than single glazing
http://www.sustainability.vic.gov.au/resources/documents/ESHousingManualCh05.pdf
So which chart do you believe?
Either way, DG is not cost-effective for retro-fitting, whereas awning blinds, roller shutters or pergolas are much cheaper and aparently more effective.
Posted Wednesday 9 Feb 2011 @ 6:32:00 am from IP # -
SteveJ
MemberJeff, those figures are Process Energy Requirement (PER) - a measure of the energy directly related to the manufacture of the materials. Unfortunatly the GER is highly variable and includes a bunch of location specific costs such as transport to site, local infrastructure/ labour costs etc. etc.
I guess the important point I am trying to make is that quality glass has a very long life, it is highly durable, very low maintenance can be easily reused/recycled (granted only a 20% PER saving on recycled glass) . Reuse of a material can reduce the PER by 95% though and glass is a prime product for reuse. The labour costs increase with reuse of materials, but I see work creation as a positive spin off rather than a negative.
Steve
Posted Wednesday 9 Feb 2011 @ 7:11:35 am from IP # -
tullera182
MemberI like glass - with a few conditions.
One of the biggest problems I see on the Far North Coast of NSW is that glass is not always openable. The general case around here is that in new houses only 1/4 - 1/3 of the "window" allows air in or out of the house. So the window can't be used to access cooling breezes, not adequately anyway.
Aspect for windows has more to do with the house facing the street than where the sun will be at any particular time of day or year so often there are huge windows facing directly west or north with no covering worth mentioning in summer. = massive heat gain for the house.
Half the north side of my house is louvered. The louveres are shaded during summer days and opened as soon as the sun goes down or as soon as a breeze comes, usually from the south to help the house cool. In winter the windows allow the sun in to warm the house.
Other windows around the house are likewise shaded from summer sun and used to help cross ventilation when appropriate.
Posted Wednesday 9 Feb 2011 @ 7:25:26 am from IP # -
SteveJ
MemberBuzzman, no maths please I am a duffer also and get easily lost in the numbers..... I agree that any poorly designed window (or window wall) is a grossly ineffective way to go and sadly the "modern housing design and the people who live in them" that you refer to are guilty of taking aesthetics over function option, in such instances glass is a very poor choice. Well-insulated and appropriately shaded glass (industrial level double glazing) that is functional and adaptable to suit not just seasonal but daily variations will provide a low tech and comfortable house. I don't see heat gain as an issue as it is easily controlled and as pointed out heat loss can also be reduced fairly easily. A good low-tech passive house is a bit like sailing a yacht, very interactive and requiring tweaks to get it going but very adaptable and efficient. Most people can't be arsed driving their house and opt for the easy option - the average house...(piece of junk that it is). Such houses have your static exposed glass and a huge HVAC system, neither is what I am on about nor condoning.
Steve
Posted Wednesday 9 Feb 2011 @ 8:14:19 am from IP # -
Jeffbloggs
MemberSteveJ
I'm obviously more a GER type of guy...but PER helps somewhat in a pinch. The easiest way to shorten the distance, is to bring the two measuring points together, the problem is that by doing so you don't budget correctly to get to your destination!I like the sailing boat analogy, do you mind if I use it?
I agree that a house does need to be driven, like the rest of nature it is in a constant state of change. Good house design and systems need to "change with the wind". If you don't plug those insulation holes (ie windows!) the house "boat" will sink, and fill up with unwanted climate, and then your only option will be to pump it all out via a HVAC!Posted Wednesday 9 Feb 2011 @ 9:15:42 am from IP # -
dymonite69
MemberI suspect there is maximum theoretical limit for glazing in a passive solar design. Even with 'infinite' mass e.g. a cave dug into the side of a mountain there is a point at which the exposed mass can absorb radiation and conduct it deeper without the surface heating up to uncomfortable levels
Posted Wednesday 9 Feb 2011 @ 10:16:22 am from IP # -
SteveJ
MemberJeff, go for your life if the sailing boat analogy helps. Most people only under stand stinky powerboats though
D69, in a conventional passive solar house prolonged heat gain (from whatever source) is required to heat up all the mass, a very slow process. Loss of excess heat is also a really slow process. This creates a relatively stable internal climate, not always a comfortable one though. Creating thermal mass is cumbersome, expensive and can have very high GER not to mention massive carbon footprint. Heat can be captured, stored and moved fairly easily without great lumps of thermal mass. Applying the principle of “Less is more”, I prefer to generate less volume of heat but keep it for longer, PassivHaus design principles have been developed to a high level in colder climates and are just as useful here in Australian cooler climates, there is an tremendous efficiency gain in doing it that way. In a house that lacks thermal mass one needs retain heat in a different manner- super insulation i.e. like a thermos flask. Such a house design is basically like a glass-fronted thermos, heat gain can be achieved easily but retaining it is of greater importance. The insulation value of the glass is of great importance and value, heat gain is secondary, albeit still significant. You can incorporate a thermo-siphoning solar hydronic heating system into the house to boost heat gain. Such a building needs glass.
Back to the double-glazing and its key function “insulation”. With north facing elevations you need to achieve passive solar heat gain through winter and insulation (all year round), to achieve this you need to use glass with a low U-value and high solar heat gain coefficient. The best option for this is inert gas filled double glazing with clear glass on one side and Low-E glass on the other i.e. the glass I have in my place has a U value of about 1.7 and a SHGC of 0.7. In summer there is protection on the north elevation with the use of extended eaves and a variable pitch solar pergola and a whole bunch of cross flow ventilation stuff also ( full awning windows, stackable doors, floor vents etc).
Steve
Posted Wednesday 9 Feb 2011 @ 11:58:40 am from IP # -
Buzzman
MemberSteve
Sorry about the maths, I am equally incompetent in that area!
My point was that the DG is only between 10-40% better than SG depending on whose stats you believe.
A pergola or external shading performs better than both.
So I see DG as a "new build" option only, at which time it is only about 50% more expensive than SG to install.
What I'm really saying is that in our climate, where keeping heat IN is not so much of anissue as it is in the northern hemisphere, single glazing, an awning blind, and maybe heavy drapes with a pelmet would probably be cheaper than DG, especially in a retrofit.
Posted Wednesday 9 Feb 2011 @ 12:08:06 pm from IP # -
dymonite69
Member"D69, in a conventional passive solar house prolonged heat gain (from whatever source) is required to heat up all the mass, a very slow process."
Actually the solar radiant transfer is much more intense than the consequent release of heat. The limiting issue is the ability for the radiant energy striking the surface to conduct throughout its thickness.
When the sun sets, the temperature gradient is much more gentle.
Surface area of exposed mass is an important consideration more than just the total volume.
Transfer of convected hot air is effective but the energy content is low. Not much of it will be stored into the building fabric after sunset.
Superinsulation to Passihaus standards require 1 foot thick walls. This requires additional building material and floor area. It is not a cost neutral solution.
Posted Wednesday 9 Feb 2011 @ 12:10:02 pm from IP # -
SteveJ
MemberBuzzman, at about $400 m2 for basic DG I have no doubt that it would be more cost effective in both new and retrofit, it's only money though, I suspect it will pay for itself in several ways.
D69, I am a big fan of hydronic heating systems, I would still use it if I lived in your cave. Is there such a thing as cost neutral solutions
I guess in urban areas the land values make this an important consideration.Steve
Posted Wednesday 9 Feb 2011 @ 12:41:02 pm from IP # -
Buzzman
MemberIf you require privacy you need to supply coverings for your windows.
If you need to provide coverings for your windows why not make them heavy drapes with pelmets and maximise the energy efficiency?
So not having to buy something 'extra' makes this 'cost neutral' - or almost....
Posted Thursday 10 Feb 2011 @ 4:08:26 am from IP #
