Browse Forums Windows & Doors Re: U-value vs SHGC & double glazing 21Nov 23, 2008 5:14 pm "Now, supposing a house to have a southern aspect, sunshine during winter will steal in under the verandah, but in summer, when the sun traverses a path right over our heads, the roof will afford an agreeable shade, will it not?" -- Socrates, ca. 400 BC Re: U-value vs SHGC & double glazing 25Nov 24, 2008 8:54 am "Now, supposing a house to have a southern aspect, sunshine during winter will steal in under the verandah, but in summer, when the sun traverses a path right over our heads, the roof will afford an agreeable shade, will it not?" -- Socrates, ca. 400 BC Re: U-value vs SHGC & double glazing 27Nov 24, 2008 10:08 am "Now, supposing a house to have a southern aspect, sunshine during winter will steal in under the verandah, but in summer, when the sun traverses a path right over our heads, the roof will afford an agreeable shade, will it not?" -- Socrates, ca. 400 BC Re: U-value vs SHGC & double glazing 33Nov 24, 2008 3:55 pm EcoClassic I you mean storage in the building fabric I can't see it... even if you did have enough storage, it would deplete to zero as the day/night wore on without any control. Used to have night storage bank - same thing basically, hot when you don't need it, not hot enough when you do. On average it's great... Radiant gain from solar energy during the day is 10x convective heat loss at night. Why wouldn't this be enough? Thermal mass materials can store quite a lot of heating energy without reaching uncomfortable levels. It's why underground houses in Coober Pedy can moderate temperate extremes regardless of season. Re: U-value vs SHGC & double glazing 34Nov 24, 2008 4:57 pm dymonite69 EcoClassic I you mean storage in the building fabric I can't see it... even if you did have enough storage, it would deplete to zero as the day/night wore on without any control. Used to have night storage bank - same thing basically, hot when you don't need it, not hot enough when you do. On average it's great... Radiant gain from solar energy during the day is 10x convective heat loss at night. Why wouldn't this be enough? Thermal mass materials can store quite a lot of heating energy without reaching uncomfortable levels. It's why underground houses in Coober Pedy can moderate temperate extremes regardless of season. 10x solar energy in during the day versus losses at night is not enough. Firstly, winter days are short. You probably only get effectively 6 hours of equivalent "full" sunlight. Therefore you need 3x the input just to match the window loss. However, the windows are the only source of solar energy and needs to counteract it's night time losses and the night time losses of all the walls and ceilings. So the house doesn't heat up enough. Now if you can half the U value of the windows, you start getting a net heat gain. In summary, double glazing is the way to go. Demolition August 2009, Construction Started September 2009, Completed December 2010 Re: U-value vs SHGC & double glazing 35Nov 24, 2008 5:02 pm dymonite69 EcoClassic I you mean storage in the building fabric I can't see it... even if you did have enough storage, it would deplete to zero as the day/night wore on without any control. Used to have night storage bank - same thing basically, hot when you don't need it, not hot enough when you do. On average it's great... Radiant gain from solar energy during the day is 10x convective heat loss at night. Why wouldn't this be enough? Thermal mass materials can store quite a lot of heating energy without reaching uncomfortable levels. It's why underground houses in Coober Pedy can moderate temperate extremes regardless of season. But what about radiant heat losses through the night... aren't they huge? They were in my home... (Albury then) - ffffreezing. "ECOECO" At 'EcoEco', we design windows, we design the best windows, we do it for you, so that when you’re happy we are happy. Tel. 1800 326 326 Re: U-value vs SHGC & double glazing 36Nov 24, 2008 5:40 pm Regardless of all theories.
A poor frame and single glazing is a cold surface which causes discomfort. It feels like sitting beside an open frigde and even with heavy drapes the cold sneaks up on you Everyone around here who has changed to double glazed PVCu or timber windows from single glazed wood or aluminium (without having changed anything else in the house!!) is going on about how much warmer the house is Theory is one thing, the real physical experience is the other Re: U-value vs SHGC & double glazing 37Nov 24, 2008 5:54 pm Casa2 10x solar energy in during the day versus losses at night is not enough. Firstly, winter days are short. You probably only get effectively 6 hours of equivalent "full" sunlight. Therefore you need 3x the input just to match the window loss. However, the windows are the only source of solar energy and needs to counteract it's night time losses and the night time losses of all the walls and ceilings. So the house doesn't heat up enough. Now if you can half the U value of the windows, you start getting a net heat gain. In summary, double glazing is the way to go. You are right, there is no such thing as a free lunch. You will eventually need supplemental heating. My question is how much heating energy will be offset by double glazing. Apart from the dead of winter there is a much less requirement for heating (if at all) with a passive solar design. Therefore the main advantages with insulated glazing is for a fraction of the year which becomes even less once you add window coverings. On the other hand, if you wish to completely prevent heat loss then even triple glazing won't achieve this. Not even if you were to decide to have no windows in your house! Regardless of design, it is impossible to achieve a zero energy dwelling by passive means alone. You will always need some kind of additional heating input. The question is not whether insulation works but how far much you can save in heatings costs for each incremental improvment you make to your building envelope. Re: U-value vs SHGC & double glazing 38Nov 24, 2008 5:59 pm windowexpert Regardless of all theories. A poor frame and single glazing is a cold surface which causes discomfort. It feels like sitting beside an open frigde and even with heavy drapes the cold sneaks up on you Everyone around here who has changed to double glazed PVCu or timber windows from single glazed wood or aluminium (without having changed anything else in the house!!) is going on about how much warmer the house is Theory is one thing, the real physical experience is the other True if you were to snuggle up close to an uncovered window on a winter night or actually leant against the pane Most people don't this. If you stay within reasonable limits of the external envelope the ambient air temperature is nowhere like that experienced near the window itself. The effect is lessened even more with a reasonably fitted window covering. Moreover, there is enough radiant heat from the interior structure to provide adequate comfort. Part of the discomfort near a sunless window is that there is no significant radiant heat approaching from that angle. That is negated the further away you move from it. Re: U-value vs SHGC & double glazing 39Nov 24, 2008 6:32 pm dymonite69 , it is impossible to achieve a zero energy dwelling by passive means alone. You will always need some kind of additional heating input. Your body, with its metabolism, provides a heat input, as does any electrical or gas appliance you use. I seem to remember reading about houses that can stay warm enough merely with those heat sources. I used to argue with my wife about that when we were stuck in a rental with only electric heating. She would go round turning off unused lights and so-on to "save energy" and would not listen when I told her it would merely cause her to need to turn the heater up to use an extra amount of power exactly equal the amount no longer being burned by the lights . Still, those amounts are miniscule compared to the total amount used on heating. "Now, supposing a house to have a southern aspect, sunshine during winter will steal in under the verandah, but in summer, when the sun traverses a path right over our heads, the roof will afford an agreeable shade, will it not?" -- Socrates, ca. 400 BC Re: U-value vs SHGC & double glazing 40Nov 24, 2008 6:45 pm russell dymonite69 , it is impossible to achieve a zero energy dwelling by passive means alone. You will always need some kind of additional heating input. Your body, with its metabolism, provides a heat input, as does any electrical or gas appliance you use. I seem to remember reading about houses that can stay warm enough merely with those heat sources. Incidental heat from other domestic appliances can be significant but I am not aware that this can provide the only source of heating energy in extreme climates. Again it is a matter of proportions. Just turning on a stove top or oven might be quite adequate for a mild climate. The opposite would be true in densely populated structures such as office buildings. Human activity, lighting and computer stations will require systems to actively prevent the building from overheating. This is one of the reasons I decided to go overseas for my double glazed windows. As the builder indicated, he's worked on many upmarket builds, these were the most well… 13 19841 As a tradesmen get a private inspector although I don't think there worth it in their profession themselves the reminder they serve to the tradesmen doing the work is… 3 27756 |