(doesn't it look like a face?)
My point is that I drew the windows as the eyes of my happy house.
And, it's true. The only place we can look out and see outside, are the windows.
Windows are transparent, and their purpose is for us to see the pretty scenery outside of our homes, peek outside to see who is ringing our doorbell, allow sunlight to come into an office building. Basically allowing us to still be connected with our outside environment without being outside.
Despite the aesthetic appeal of windows, their purpose is much more than just being the 'eyes' of a building/home.
Rather than being a transparent barrier, they act more like the membrane of a cell: by which heat is being diffused through.
Living in Arizona, we want our windows to have the least amount of heat transfer. Why? Because it's so HOT! (Especially in the summer!!) An effective house in the summer in Arizona would have windows with a low U-factor, a low solar heat gain coefficient (SHGC), and a low air leakage rating.
The U-Factor is what evaluates the direct heat transfer. It is the rate through which house openings (window/door/skylight) conduct heat flow, measured in BTU/hr-ft^2-oF. Lower U-factor means less (non-solar) heat flow conducted, and vice versa.
The solar heat gain coefficient (SHGC) is what evaluates the blockage of solar radiation through windows. When radiation passes through a window, it gets released as heat inside the home. (bad for Arizona summers!!) Similar to the U-factor, having a lower SHGC means less solar heat transmitted.
For colder places around the world, it might be a good idea to have a higher SHGC... This way the radiation from the sun won't get rejected by the windows, and in turn will actually help keep the warmth inside.
The air leakage rating evaluates the rate of air movement around the house openings, caused by the pressure differences between inside and outside of the space. It is measured in cfm/ft^2. Also like the previous ways of evaluation, the lower the air leakage rating is, the tighter the window will be, and thus less heat will be transferred inside the home.
Other solutions/mechanisms of reducing heat transfer through windows is adding more panes of glass, or putting a coating on the glass.
-In order to reduce the heat transfers, you can add 2 panes or even 3 panes of glass, instead of 1. The space between the panes are then filled a gas (usually argon), as it has a low heat transfer property. This way the heat from the outside (or even from the inside, if it's winter) will be buffered. Also, the gas helps prevent fogging between the panes.
-Coatings on glass are also effective in lowering the U-factor. Low-e coatings are microscopic (nearly invisible) metal or metallic oxide layers. Different types of coatings will allow different transmissions of solar gains (low, medium, high). Despite of course its higher price, it reduces energy usage at a higher benefit. These coatings also effectively reduce UV radiation as well (can be 70%!).
I hope you got my pun in my title... :D but, definitely windows became so much more than what I thought they could be!
I found all this information from "Sustainable Choices in Luxury Fenestrations" in the June 2014 edition of Architect Magazine.
Despite the aesthetic appeal of windows, their purpose is much more than just being the 'eyes' of a building/home.
Rather than being a transparent barrier, they act more like the membrane of a cell: by which heat is being diffused through.
Living in Arizona, we want our windows to have the least amount of heat transfer. Why? Because it's so HOT! (Especially in the summer!!) An effective house in the summer in Arizona would have windows with a low U-factor, a low solar heat gain coefficient (SHGC), and a low air leakage rating.
The U-Factor is what evaluates the direct heat transfer. It is the rate through which house openings (window/door/skylight) conduct heat flow, measured in BTU/hr-ft^2-oF. Lower U-factor means less (non-solar) heat flow conducted, and vice versa.
The solar heat gain coefficient (SHGC) is what evaluates the blockage of solar radiation through windows. When radiation passes through a window, it gets released as heat inside the home. (bad for Arizona summers!!) Similar to the U-factor, having a lower SHGC means less solar heat transmitted.
For colder places around the world, it might be a good idea to have a higher SHGC... This way the radiation from the sun won't get rejected by the windows, and in turn will actually help keep the warmth inside.
The air leakage rating evaluates the rate of air movement around the house openings, caused by the pressure differences between inside and outside of the space. It is measured in cfm/ft^2. Also like the previous ways of evaluation, the lower the air leakage rating is, the tighter the window will be, and thus less heat will be transferred inside the home.
Other solutions/mechanisms of reducing heat transfer through windows is adding more panes of glass, or putting a coating on the glass.
-In order to reduce the heat transfers, you can add 2 panes or even 3 panes of glass, instead of 1. The space between the panes are then filled a gas (usually argon), as it has a low heat transfer property. This way the heat from the outside (or even from the inside, if it's winter) will be buffered. Also, the gas helps prevent fogging between the panes.
-Coatings on glass are also effective in lowering the U-factor. Low-e coatings are microscopic (nearly invisible) metal or metallic oxide layers. Different types of coatings will allow different transmissions of solar gains (low, medium, high). Despite of course its higher price, it reduces energy usage at a higher benefit. These coatings also effectively reduce UV radiation as well (can be 70%!).
I hope you got my pun in my title... :D but, definitely windows became so much more than what I thought they could be!
I found all this information from "Sustainable Choices in Luxury Fenestrations" in the June 2014 edition of Architect Magazine.
Hi Victoria! Wow, so much work goes into putting in a window. I heard also that it depends what side of the building they are on? Say, for instance, it's one of those houses on the mountains where it might still pretty hot but the sun doesn't always hit it in the same way, does it matter where the windows are, and would the windows on different sides of the house have different components?
ReplyDeleteIt is very probable that differing windows will have different properties. As for positioning, positioning would matter for direct solar radiation, but otherwise for all-around warm/hot air, the outside temperature would be fairly consistent and may call for a specific ideal U-factor.
DeleteHi Victoria!
ReplyDeleteThis was such a helpful post (especially since I need to get new windows for my house...now I know what I'm looking for)! When designing a structure, does an architect place any emphasis on the type of windows being used, or are they more concerned about the placement of the window? I guess what I'm asking is, where is the balance between function and aesthetics?
Different architects have different ideals, and of course there is also consideration for what the client's ideal would be... This balance between function and aesthetics is still a concept I am still looking into :)
DeleteFor different architects the answer will be different, but as for what I've heard so far at my firm, they are concerned upon the placement of the window, or maybe a shade structure to balance out the exposed interior. Even if a window is aesthetically placed, with the 'right' type of window properties, sunlight will still enter the home, affecting the living qualities (maybe blinding people at a certain time of day). So, even with aesthetic decisions, a functional lens is applied, to perhaps find the loophole where the aesthetic design can be preserved while still being effective in its functionality.