Passive Solar Design Principles should be included in all new house builds | homestar
Passive Solar Design Principles should be included in
all new house builds
It seems that ever since the invention of electricity and fuel-based heating and coding systems, we have deliberately ignored basic principles of good design.
Thankfully, recent research, policy, and the development of assessment frameworks such as Homestar – through the use of mandatory minimum in EHC6 and EHC7 – are all inviting us to ‘get the basics right’ before being carried away with other design features.
We are talking here about the general design of the floor, walls and roof incorporating principles of orientation, insulation, glazing, solar gain and solar shading, thermal mass and ventilation.
The vast majority of new homes being built still largely ignore these basic principles. While site sizing, shape and orientation can sometimes create challenges, it does not mean that it’s impossible. The house design simply can be tweaked to make best use of the conditions. Any slight increase in cost can be offset elsewhere in the design and modern/modular construction techniques allow further cost efficiencies.
Get these basics right first:
Orientation, location and layout should be considered from the beginning of the design process – ideally, from the time the site is being selected.
For maximum solar gain, a building will be located, oriented and designed to maximise window area facing north (or within 20 degrees of north). (Reference: Level.org.nz)
Insulating to code is not enough. Building code represents nothing more than the minimum legal requirements. For the majority of houses using traditional building materials, it would be of benefit to go at least 50% above, or even double code requirements in terms of insulation levels.
‘Thermal mass’ is the capacity of a material to store heat energy.
In building terms, it reduces temperature fluctuations and improves indoor comfort by absorbing heat when the ambient air temperature is hotter than the mass, and vice versa by releasing heat when the ambient air gets colder.
For passive heating, thermal mass works by exposing a high-density material in the building’s interior – such as concrete or stone – to direct sunlight. Often, this will be a concrete slab floor, though it can also be a wall or a specially designed thermal mass element such as a Trombe wall. The sun’s warmth is absorbed during the day and then radiated into the home as the temperature cools at night.
For passive cooling, thermal mass is combined with ventilation – so heat is absorbed during the day, then ventilation is used to dissipate the heat when it is released at night. (Reference: Level.org.nz)
Windows and doors can account for more heat gain or loss than any other element in an insulated building envelope. A well designed glazing system can improve internal daylight levels, reduce glare, and help maintain thermal comfort by reducing heat gain and loss.
Heat is gained and lost through the glazing and through the frame, so it is important to consider both together. It is also important to consider both the glazing unit’s insulating properties and its efficiency at letting solar radiation into the building (this is known as solar heat gain coefficient). (Reference: Level.org.nz)
Options for consideration:
- Low E coating: Low-e glass has a thin, transparent film that reflects heat. When the interior heat energy tries to escape to the colder outside during the winter, the low-e coating reflects the heat back to the inside, reducing the radiant heat loss through the glass. The reverse happens during the summer time. (Reference: PPG Glas Education Center)
- Double or triple glazed windows: Insulates your home against extremes of temperature, reduces noise from outside and reduces condensation.
- Thermally broken frames: These window frames reduce heat loss by using either polyamide insulating thermal strips or an insulating polymer. The thermal break provides an insulating barrier minimising the transfer of energy (heat or cold) via the frame. Timber frame windows also offer good insulation performance.
Now, that you have done what is necessary to maximise the absorption of the sun’s heat during the winter, external shading is important to avoid overheating in the summer.
There are many options for external shade. It’s important that each is designed to take account of the sun paths at the site at different times of the year, ensuring the sun penetrates through the windows during its lower winter angles, but not during its higher summer angles.
Several options could be considered:
- Larger eaves or other fixed overhangs.
- Awnings reduce sun when they are in position. They should be light in colour to deflect more heat. Retractable awnings will admit sunlight when in retracted position.
- Fixed and moveable screens and shutters provide an excellent solution for low angle morning and evening sun as they can be moved away to admit light when not required.
- Horizontal, fixed louvres should be angled to the noon mid-winter sun angle and be spaced correctly to admit winter sun.
- Pergolas covered with deciduous vines provide very good seasonal shading.
- Trees and shrubs provide excellent shading. Deciduous trees provide shade in the summer and admit sun in the winter. (Reference: Level.org.nz)
Now that we have got our basics right, we can focus on improving other areas such as water efficiency, materials selection, renewable energy technologies, etc. The list is long but Homestar does a good job of ‘framing the questions’ and providing a check list for implementation in practice.
It’s time for all of us to just make it happen!
Energy Efficient Features Justify Premium Price
Realestate.co.nz and Homestar survey reveals almost all respondents believe how your home is climate controlled is the major price tag decider.
More than 90% of home buyers believe that high levels of insulation and efficient heating and cooling justifies a home having a price premium. When it comes to specific home features such as double glazing, solar panels, efficient energy fixtures and water conservation systems, more than half of home buyers agree that these contribute to a price premium.
These attitudes are revealed in a recent survey undertaken by Realestate.co.nz in association with Homestar to gauge the features people regard as important when looking for a home to buy. The first such survey was conducted last year, with 1,725 respondents. This year’s survey was much larger, with 5,980 people taking part. “It is clear that sustainability and environmentally friendly features are increasingly important to home buyers,” says Paul McKenzie of Realestate.co.nz.
“It’s good news that Kiwis are taking such a strong interest in how well their home performs. We’re seeing a real appetite for good advice and information,” says Leigh Featherstone of Homestar.
Prospective home buyers surveyed rated house orientation to maximize sunlight as the single most important home feature, with 86% of respondents rating it as important. A high level of insulation was rated important by 82% of respondents. Having specific energy-efficient features such as solar panels and double glazing is important to nearly half the respondents, while 36% also consider whether the house is built from sustainable or environmentally friendly materials.
Nearly 30% rated water saving features such as a rain water tank as important.
After sun exposure and insulation, the home feature rated most important by home buyers is where you put your car – off-street and covered car parking both rated as important by nearly 75% of respondents. Other home features considered crucial by over 50% of respondents include, in order: number of bedrooms (3 or more), ample storage space, indoor/outdoor flow, a quiet street location, an outdoor entertaining area and open plan living.
The annual Realestate.co.nz survey provides key insights into home buying preferences with quantified results sometimes contradicting popular beliefs such as the supposed importance of homes having a gourmet kitchen. In fact, kitchen design is only rated as important by 51% of respondents.
Realestate.co.nz is the country’s most comprehensive property listing website, profiling listings of licensed real estate agents with more than 100,000 listings covering residential, commercial, business and farms for sale.
The most recent issue of the NZ Property Report, a monthly report of housing market activity compiled by Realestate.co.nz, can be found along with additional analysis of the property market at www.unconditional.co.nz, the news and information website for New Zealand real estate.
Practical advice and information on improving home performance, including a tool to rate your home are available at www.homestar.org.nz.
Home performance components that contribute to a premium price:
- High levels of insulation
- Efficient heating and cooling
- Solar Panels
- Efficient energy & water fixtures
- Double Glazing
- Water conservation systems
- An independent rating and official certificate for the homes
- Low energy lighting
- Fixtures and fittings with low levels of toxicity, e.g. low VOC
Add value with myHomestar
A spate of home building and renovation TV shows, such as The Block and Mitre 10 Dream Home, has inspired many Kiwis to tackle a home improvement job on their own patch.
Not only are renovations a wonderful opportunity to make over your home aesthetically, but also to modernise the functional elements of your house, such as insulation or water-efficient plumbing and fittings.
Buyers are re evaluating their priorities when it comes to desirable home features, with a recent survey by realestate.co.nz indicating that the majority of respondents would pay a price premium for specific eco features such as efficient heating and cooling systems, double glazing, and energy and water efficient fixtures such low flow taps and high energy star rated appliances.
If you are renovating your home, myHomestar can provide you with independent advice for eco improvements to your home, which will make it more comfortable to live in and may command a higher price when it comes time to selling.
View full article:
– See more at: http://www.homestar.org.nz/newsroom/add-value-myhomestar#sthash.2jw0h4PH.dpuf
Note: the issue of home health is becoming more popular these days thankfully. Cold damp housing accounts for major health problems such as asthma, respiratory disease and more… if you want to no more about how to improve your home rating check out the link to the right of this article and do the test, rate your home for efficiency and then make the necessary improvements. To gain a top rating other things are taken into consideration like distance from town, ( can you walk as opposed to using your car and other transport) undercover cloths line etc. (saving on clothes driers) you may be pleasantly surprised and you will definitely get some great tips
Let me know what you think… please leave a comment for me below (and then go ahead and hit that “Like” button!)