The Pyramid For Building & Renovating Smarter
Eco living is not a fad, in fact, it’s here to stay, and people are getting more serious about it. Builders, architects, and designers are becoming more conscious of the effects of eco-smart designs, and homeowners realize the benefits to their wallets and the environment.
All house plans submitted to council these days must meet a minimum energy star rating.
The 10 points in the house/pyramid highlight the foundation elements and everything else that can be actioned as a cost/priority when building or renovating a home so that it is comfortable, less maintenance, environmentally friendly, energy-efficient, and overall a more sustainable house.
First of all, it’s important to understand, sustainability. A wonderful foundation of information for this is Passive House. It’s a very hard standard to satisfy, but if you get halfway there, you will be in the right place.
1. House plan
For a new house, sketch the house plan. Position living spaces, such as the kitchen, dining and lounge rooms on the north side, and utility areas and bedrooms in the south. By doing this, you ensure that living spaces benefit from the winter sun and the bedrooms stay cooler in summer. Remember that good design or bad design will cost the same amount of money! In a retrofit, implement shading on north facing brick walls, extend eaves, put in place window shutters, to allow winter sun in, and disallow summer sun. Install deciduous trees and creepers which may help you to protect thermal mass in summer and expose thermal mass in winter.
2. Summer and winter
Always consider the impact that the seasons have, particularly summer and winter, on the house. How will your design deal with the hot summer sun? And how will it handle cold winter winds?
Make sure you have external shading on the north side to protect interior living areas from the harsh summer sun. This approach will still allow the winter sun into your house when it starts to become a bit dark and dreary indoors as well as outside. This will also reduce the amount of artificial light needed indoors during winter.
3. Gaps and cracks. Air tightness
The structure of a house is made up of external walls, the ceiling, and the floor. As these enclose all of the internal spaces, the structure is also called the ‘building envelope’ If you are serious about conserving energy, you must make sure that the building envelope (or structure) is as tight as possible. There are plenty of holes, gaps, and cracks in a house. So, before plastering it is important to seal these openings and prevent unnecessary energy loss from the house.
Every house, leaky or not, needs adequate exhaust ventilation. This is necessary to get rid of indoor pollutants, as well as moisture from kitchen and bathrooms. In most cases exhausted stale, polluted and moist air is replaced by fresh outside air, coming in through holes and gaps in the building. This outside air is called ‘make-up air’, as it makes up for the air which was exhausted out of the building. Regarding indoor air quality, this scenario sounds all right. The only problem, however, is that with this stale air, also the energy (from heating or cooling) leaves the building at the same rate.
Finding the balance between having this fresh air coming in, stale air going out, and losing all this expensive energy, is probably the most important aspect of a healthy, energy efficient house. Sealing the building envelope tight enough, so little energy escapes, and at the same time providing the right amount of natural infiltration, requires implementing some smart strategies. The good news in all of this is that it can be done very cost effectively in both new construction and existing buildings.
Finding the right balance between energy efficiency and good indoor air quality is done through a performance test on the building envelope. This test is non-intrusive and takes only a couple of hours to complete. The process of air ‘in and out’ is often expressed as Air Change per Hour (ACH). As air infiltration relies on a pressure difference between inside and outside, the process also relies on the level of pressure difference. Pressure is measured in Pascals (PA), with 5 Pascals being a very light breeze and 50 Pascals being a roughly 30 km/hour wind blowing against the building. 1 ACH@5Pa, therefore, means that all the air in a building is replaced by outside air over a period of one hour, during a very light breeze. The performance test on the building envelope creates this pressure difference and measure the amount of air coming back into the building through holes and cracks.
A good average ACH for Australian homes should just above 0.5ACh@Ambient Pressures, although it is always crucial to look at every building individual, as there are many variables which could compromise good indoor air quality. If a homeowner would like to have their home leak less than this 0.5ACH, it is a must to install a mechanical ventilation system with energy recovery capabilities ( see step 6 of the pyramid) Heating, cooling and fresh air.
4. Insulation consistency
There are several types of insulation available on the market, including batts, reflective foils, blow-in “fluff”’, and sheet insulation. Foils reflect outside heat in summer and, to a much smaller degree, can keep heat in the house in winter. Batts and blow-in insulation form a barrier against cold, as well as heat, through the air they trap. The more still air the product can hold, the better it will perform.
And whatever insulation you choose, make sure it is installed correctly. Any gaps or holes in the insulation barrier could result in air leakage and energy loss. If you opt for downlights in the ceiling, remember that each light creates a ‘hole’ of 150 mm in diameter in your insulation cover. This is a building regulation to prevent overheating of light fixtures and could result in considerable energy loss.
5. Double glazing
Double-glazed windows are a good investment for energy efficiency; they also allow for better noise control. Different types of films and coatings are available to increase the energy efficiency of windows.
Double-glazed windows/doors are an expense item, so do your homework and bear in mind that the long-term savings should be considered favorably against the initial cost.
In step 3 we talked about the importance of ventilation when building a well-sealed building envelope. If you decide you want the ultimate in energy efficiency and go tighter than 0.5 ACH@5PA, you should consider installing a whole house mechanical ventilation system with energy recovery. This type of ventilation system allows for a super airtight building envelope. It provides 24/7 fresh air to the living areas and bedrooms and exhaust 24/7 from the bathrooms, kitchen and utility areas. It is usually ducted throughout the house, or, with apartments, through-the-wall systems are also available. The energy recovery takes place inside the actual system and is usually over 80% efficient. There are many websites on energy recovery ventilation system and some companies sell in Australia. When investing in a quality building envelope (well sealed, well insulated, double glazed) a whole house mechanical ventilation system brings it all together.
7. Heating, cooling, and fresh air
Having done everything to seal and insulate the building structure, it is time to decide how to heat or cool your house.
If you have followed the preceding steps in the upside down the pyramid to plan, then you will need very little heat in winter and almost no cooling in summer.
Perhaps a small, energy-efficient, split system heat pump in winter and a couple of ceiling fans in summer may be all you need.
And because the bedrooms are on the south side of the house, they’ll be cool in summer.
Then, with the money saved from heating and cooling, think of installing a heat pump hot water system.
If your budget allows for it, consider a mechanical ventilation system for the entire house. Especially in a well-sealed house, this system will provide fresh, filtered air all year round with minimal loss of energy.
It is also effective in reducing high levels of humidity, which in turn controls dust mites and mold growth.
Get these things right and then you can move onto the other things in the upside down pyramid, to help you cost effectively move to a more energy efficient home.
8,9,10 Solar, lighting, appliances and efficient hot water systems
All these things are great and a complete no brainer when there are subsidies available, or if these things break and need replacing, Solar Panels and heat pump hot water systems, with subsidies can move further down the pyramid, from a cost perspective and they can also turn your home into a net contributor to the grid when you have your building envelope right.
John Konstantakopoulos & Jan Brandjes