Glass can make a real difference

Posted by Benjamin Close on February 10, 2009 under Country Living | Be the First to Comment

One thing a lot of people are unaware of is just how much difference a good glass can make to their house. Many people think of glass as just being something to look through. But glass is much more than that. Glass is:

• A wind barrier
• A heat barrier
• An Insulator
• A protection mechanism
• A sound barrier

More and more people are building houses with lots of glass. They do this to increase their views, to make the house feel more open and to make a house feel more homely. Take our house for example. Our house has 57.84m2 of glass consisting of glass doors and windows. The entire living area of our house is 224m2. Hence we have a lot of glass.

All this glass is great for view, not so great for cleaning and when it comes to heating and cooling could be a disaster. You see glass is a relatively poor insulator. On a hot day put your hand up to the window and feel just how hot it is. Heat comes through standard glass (normally 4mm float glass) at a rate of 1 watt per m2, per degree celcius. Hence if you had one window of 1 m2, and the temperature outside was 1 degree hotter than inside, you’ld need to put in 1 watt worth of cooling to prevent the room getting hotter, per hour.

So with a house with 57.84m2 worth of glass, we’d need 57.84 watts for every degree difference outside. So image it was 40 degrees outside. We wanted to keep the inside temperature at a plesant 26 degrees. That would require 40-26=14 degrees, 14*57.84 ~= 810 watts/hour. That’s a lot of heat you’ve got to offset! If your on solar, that’s almost 1Kw/h which is very hard to maintain!

There is however a way to make a difference. One that doesn’t need artificial cooling/heating.  There is lots of glasses around now. Each glass has different properties. There is double glassing which separates two panes of glass with either an air gap or inert gas. There’s ‘Low E’ type glasses which have a special reflective coating to prevent heat getting in, but allowing light in. There’s glass which helps knock out all the UV rays so it’s better for your eyes and doesn’t fade your furniture.

We’ve chosen to go for a glass called ‘Comfort Plus‘ glass. This glass has a much better thermal properties
as it is two sheets of 3 mm float glass with a silcon wafer sandwiched in between. Hence it effectively works like double glazing without the cost of double glazing and without the problems associated with double glazing. (Double glazing suffers from not being able to have sliding windows, weight issues, condensation issues). Comfort Plus is by Viridian glass and hence Dowell, the window maker used by Format, is able to source it (as they use viridian glass). Whilst it is a little heaver than standard glass, the benefits it has are certainly worth it. If you look at the glass comparision compared to standard4mm float glass comfort plus Clear #82:

• Blocks out 99% of all UV light
• Reduces Heat Gain/Loss by 2.3w  per m2/degree celcius/hour
• Is a thicker glass (6.38mm vs 4mm) so has better sound insulation, is more resistent to breakage
• Lets more visible light through!
• Reduces solar radiation
• Is laminated, hence it’s suitable for a medium bushfire region

So in the long run, whilst comfort plus glass might cost a little more than standard glass, the benefits outweight the downsides.

So whether your building a new house, replacing a window or extending an existing house, stop to think about the glass. It could save you a fortune!