The building envelope is the area of the home that supports structure and physically separates the elements from the enclosed space (the inside of the home) for example the walls, windows, doors, sub floor and the roof.
The purpose of this exercise is to give the example for the control of energy use within the building envelope. To create barriers to the elements of wind, rain, excessive heat and cold, frosts, snow and condensation.
THE PROCESS FOR ENERGY CONTROL OF THE BUILDING ENVELOPE THE ROOF, THE WALLS, WINDOWS, DOORS, INSULATION, ROOF VENTILATION USE AND SUB FLOOR (IF ANY)
Starting from the ground up –
The Sub Floors - If you are not on a slab you will have a sub floor, the area between the foundation and the floor. This can be a problematic area if there is not good airflow throughout the sub floor and/or if the floor is very close to the ground, you could have rising damp. Remedy – increase the amount of ventilation bricks substantially around the perimeter, this will dry out any moisture problem you can also run an AG drain along the wet side of the house.
The Walls – Generally the most common materials for the walls are brick veneer consisting of a load bearing timber frame wall with a 50mil cavity tied into brick cladding. This is an excellent and economical way of keeping the elements of nature from the internal wall and the cavity allows airflow between the two material elements of the wall, this is a good thing and that is what a cavity is designed to do. If you do have a sub floor the cavity allows air to pass up through the walls from the sub floor through the roof cavity and exhausts through the roof ventilation. If you must have insulation in your walls only contemplate a board type insulation that still allows at least a 25mil cavity between the board and the brick wall for air flow. DO NOT USE LOOSE FILL BLOWN IN CAVITY INSULATION as this brings the outside wall into contact with the inside wall, this brings with it a number of problems. It allows moisture to draw through to the inside gyprock wall, it allows brick ties to rust and wherever there are air pockets within the insulated wall condensation will form on the gyprock inside the home. This insulation is extremely difficult to remove after the fact.
The Windows – If you have an existing home – you can treat your windows which are probably only 3mil thick with a thermal insulation film, this can be professionally done or you can do it yourself, there are many types available. Or you can retrofit double glazing, Magnetite are a company that can do this www.magnetite.com.au they use optical perspex it works very well and has the added advantage of sound insulation as well.
IF YOU ARE BUILDING A NEW HOME AND WANT TO INCORPORATE ENERGY EFFICIENT WINDOWS
Double glazing is probably the best way to go however there is double glazing and then there is double glazing, what you spend will be the difference, look for quality. Ask the questions, filter the answers. Expensive however probably the best double glazed windows are UPVC framed double glazed windows made by Certainteed an American company who I believe are probably the inventors of UPVC windows www.certainteed.com.au Then you have comfort glazing or low E glazing which is 6.38mil laminated glass however if you live in an extremely cold area I would recommend quality double glazing.
The Doors – For external use always use a solid timber door the thicker the better, your external doors can contribute significantly to the waste on energy due to conduction. Make sure the door is weather sealed to all extremities. There are also UPVC and fiberglass doors available however these are extremely expensive and much harder to attain. However the small area that external doors for the building envelope approximately 1.75sqm cover, I believe a good quality thick solid timber door weather sealed to exclude air leakage is most likely best value for energy and economy efficiency.
LAST BUT NOT LEAST THE ROOF THIS IS THE AREA OF THE BUILDING ENVELOPE THAT TAKES THE BIGGEST HIDING FROM MOTHER NATURE
With constant rain, wind, storm cells, cyclones, snow, ultra violet rays from the sun, frosts, snow etc etc, the roof takes it all. So a good roof covering is essential – the best roof covering is corrugated colorbond roofing incorporating blanket insulation and an effective roof ventilation system. As a roofer with 5 decades in roofing it is my experience that the aforementioned system is the most maintenance free roof protection to the building envelope of a home. Following 3 lengths back in second place is a concrete tiled roof with sarking and an effective roofspace ventilation system. So there you have it, in my professional opinion corrugated colorbond roof first and tiled roof second. See BLOG on this site – “Corrugated Colorbond Roofing”.
WE HAVE GIVEN TWO EXAMPLES FOR ROOF COVERINGS FOR THE ROOF OF THE BUILDING ENEVELOPE WHAT ABOUT THE ROOFSPACE
Well consider the roof covering as the outside layer of the building envelope, what about the inside layer the roofspace. On the ceiling it is mandatory to have R3.5 ceiling insulation. Although not mandatory yet but pretty soon will be, there is the need for effective roof ventilation see BLOG on this site “Warning! Read Before You Design Your Next Housing Project”.
In winter the ceiling insulation will maintain most of the heat to the enclosed space (the inside of the home) however the heat loss to the roofspace becomes another problem without effective ventilation this will turn into water vapour – condensation.
In summer without effective roof ventilation the roofspace becomes a trap for excessive heat buildup, this heat radiates downwards into the home causing much discomfort to the living areas of the enclosed space causing sleepless nights and massive cooling bills.
SO FOR AN EFFECTIVE WORKING ROOFSPACE WE NEED A VERY EFFECTIVE ROOF VENTILATION SYSTEM
Universal Tile Ventilators have the best systems in the world for roofspace ventilation – Universal Tile Ventilators for tiled roofs, Smoothline ventilators for corrugated colorbond roofs.