About Your Home S Building Shell

Fact sheet 1 Your home’s building shell

Better thermal performance for renters Improving your home’s Even if you’re renting or you don’t want to make big energy efficiency changes, there are easy and inexpensive things you can do to boost your home’s thermal performance.

The Residential Efficiency Scorecard rates your These include: home’s energy efficiency.  changing to your behaviour and energy-use It does this by measuring the thermal performance habits, like keeping external doors and windows of your home’s building shell – this means how well closed it responds to changes in external temperature.  draught-proofing your home’s doors and windows This fact sheet gives you some tips for improving your home’s thermal performance.  closing internal doors so you only heat or cool a smaller zone within your home – bathrooms and laundries tend to have high air leakage rates, so About your home’s building shell keep these doors shut The building shell is the materials your home is constructed from.  installing secondary double glazing in your windows – you can buy products made from It includes walls, floors, insulation, floor coverings, plastic film that act as temporary double glazing. windows, window orientation and shading. These small changes can make a big difference to your The Residential Efficiency Scorecard looks at four energy bills. properties of the building shell. And it’s not just a matter of saving money – better  insulation, which keeps the air inside your home thermal performance can save lives. warm in winter and cool in summer Heatwaves in Victoria are responsible for more deaths  thermal mass, which affects the rate your home each year than any other natural disaster. heats up and cools down. Materials like concrete or brick have high thermal mass, and slow this Older people, very young children or people with rate down health-related risk factors like cardiac and respiratory conditions are most at risk.  windows, which are an important part of your home’s insulation. They also let in light and heat, So if you or someone in your family could be vulnerable which can be beneficial in winter, but may cause in hot weather, taking these simple steps to improve your home to heat up in summer your home’s energy efficiency will make a big difference to your health and wellbeing.  air leakage, which occurs through the many gaps between the inside and outside of your home. These include deliberate openings like wall vents and chimneys, as well as gaps and cracks that develop over time. Structural improvements – insulation Floors If you’re up for some bigger changes or you plan to Insulate timber floors with boards, batts or foil. renovate, you can make structural improvements to the building shell. This includes adding insulation. Insulation is most effective on floors that have a large space underneath – and these are also often the most Ceilings and roofs accessible. If your home doesn’t have ceiling insulation, it is relatively easy to install if you can access the ceiling Structural improvements – thermal space. mass Adding insulation will make a huge difference to the If you plan to renovate, consider adding thermal mass comfort of the home, keeping it warm in winter and cool to your home. in summer. You can do this by using high-mass materials such as If the ceiling space isn’t easy to access, consider concrete slabs, brick, mud brick, rammed earth or adding insulation when the roof needs replacing. You straw bale walls. can also install an insulated false ceiling below the actual ceiling. You still need to insulate walls with high thermal mass, but it is best to insulate the wall outside the massy part. You should use insulation with a minimum insulation value of R3.5. The most common form of insulated massy wall is known as reverse brick veneer, which has bricks on the Make sure that insulation coverage is as complete as inside and cladding on the outside. possible – even a small uninsulated area will significantly reduce the value of insulation. Structural improvements – windows If your ceiling is already insulated, you can put more Windows have two important properties: insulation on top. Sometimes loose-fill (generally  insulation cellulose) insulation moves around over time. Top it up  letting the sun in (solar gain). and even it out to provide a good layer of insulation in your ceiling. Window insulation Both the frame and the type of glass affect the Remember that if there are lighting fixtures such as performance of windows. halogen down lights in the ceiling, you need to maintain a minimum clearance between the light fitting and the insulation. Insulation guards may be required. Frames For frames, timber and plastic (PVC) generally have Some modern LED light fittings allow insulation to be the best insulation value. installed over them – check the specifications of the fitting to see what the requirements are. You can also use high-performance composite/hybrid (metal outside, timber inside) and ‘thermal break’ The insulation installation standard (AS3999:2015) and aluminium frames. the wiring rules (AS/NZS 3000:2007) provide information on the requirements. Simple aluminium frames have the lowest insulation value. Walls Walls are difficult to insulate in place, so it’s best to do Glazing it while you are renovating. Double glazing gives a much higher level of insulation than a single glazed window. If you need to replace the lining or cladding of any walls, make sure you install insulation at the same The cost of double glazing has fallen substantially over time. the last few years. If you are replacing any windows, seriously consider double-glazing. Talk to your builder about insulating other walls that may not be directly affected by the renovation, as the Double glazing may also incorporate argon gas and cost to insulate them during construction may be low E (low emissivity) coatings. Both of these improve relatively small. the insulation value of the windows, but add cost. Structural improvements – air leakage Single-pane low E glass is an alternative to double- glazing. It has some limitations, so talk to your supplier. Air leakage occurs when air inside your home is You can also add secondary double glazing to existing replaced with air from the outside. In winter, this means windows. This involves adding an additional pane of that air you’ve heated leaks out. In summer, hot air glass or plastic (such as Perspex). The secondary from outside replaces cool air inside. glazing can be permanently fixed to the current frame, or it can be removable. Exhaust fans Exhaust fans can allow a lot of air leakage. Window coverings Curtains and other window coverings also provide You can install exhaust fans that have closable louvres window insulation. to reduce unwanted air leakage.

For the best effect, the curtain or blind should create a You can also purchase products that cover horizontally still air space between the covering and the window. mounted exhaust fans and provide flaps that seal the fan outlet when it is not in use. One of the most effective ways to do this is with heavy floor-length curtains with pelmets. Chimneys Open chimneys can lead to large amounts of air Solar gain leakage. Windows can let in lots of heat from the sun. If you want to use your fireplace, you can fit a damper This can help to warm your home in winter, but it can that blocks the chimney when it’s not in use. be detrimental in summer. You can also block the chimney permanently if you North and west-facing windows generally add the most don’t want to use the fireplace. heat, while east-facing windows tend to have less impact. Door and window seals New window frames and sliding door frames generally South-facing windows don’t get much direct sun in have weather seals. Victoria. You can apply seals to existing window and door As well as the location of the windows, the type of frames. There are many products for different glass and any external shading will also affect heat situations. gain. If you’re looking for a less-permanent solution, you can Tinted glass reduces heat gain. This is great for stop gaps at the bottom of doors with a door snake. summer, but also reduces beneficial heat gain in winter. Wall vents, ceiling vents and vented skylights Homes built before the 1980s often incorporated wall or Note that double glazing does not generally reduce the ceiling vents. amount of solar gain. These have not been required in the building code for External shading new homes for many decades. In most cases, you can External shading takes two forms: fixed and adjustable. seal or remove these vents.

Eaves are effective on north-facing windows, as they Vented skylights incorporate a permanent opening, can be sized to allow sun in winter when the sun is low usually covered by flyscreen or mesh. These are in the sky, and block it when it is high in the sky in generally found in bathrooms. summer. You should be careful about modifying ventilation in Eaves are much less effective on east and west-facing bathrooms and other high-humidity areas. Install windows. alternative ventilation such as exhaust fans if you remove or seal fixed ventilation. Vertical shading is a better solution for these windows, including external awnings, shutters or roller blinds. If you plan to use an unflued heater in a room, do not Skirting gaps remove or seal fixed ventilation. Unflued heaters Air leakage can occur in gaps between the skirting and release significant amounts of potentially harmful the floor, especially in older homes. combustion products into a room, and need minimum ventilation rates to operate safely. On a timber floor over a subfloor, there is likely to be significant leakage. Down lights Some down light fittings allow significant amounts of air On upper floors, or ground floors on a concrete slab, leakage. leakage is less likely.

This is especially true of older style incandescent down These gaps can be addressed by using a caulking light fittings and gimballed (swivel) halogen fittings. material, or you can use a filler on large gaps.

You can replace these with high-efficiency LED fittings Other places were air leakage occurs that reduce air leakage, as well as energy There are many other places where air leakage can consumption. occur.

Floorboard gaps These include pipework penetrations, pet doors or Older floorboards may develop gaps between them poorly fitting utility covers. and allow air leakage. Each site needs to be addressed individually. This is a difficult issue to solve. The simplest approach might be to install carpet.

You can try using gap fillers, but floorboards tend to shrink and expand, and bend when walked on, causing fillers to fall out.

Another alternative is to insulate the floor from below with a product that provides an air seal.