Tag Archives: Affordable

The 20/20 House – Part 1

The Gruen Eco Design blog about how to convert your dream from an energy efficient home into a reality.

My partner and I are planning to build an affordable energy efficient house for our family. So I thought I take this opportunity to write about all the things we will have to go through to get into our home. And hopefully this can give some guidance or help to others in the same position.

I do want to talk about the whole process. Starting on how we get the finance sorted, finding the right side. How to determine what rooms we need and how the house has to function for us. But also what things we have to consider during the design phase, how to find and deal with a builder. Through to the construction process and then hopefully a happy ever after move into our new dream home.

But for now, we are just at the start. So in my first blog I will talk about finance. And what you need in order to get a pre approval from the bank, so that you can start actively looking for the right site.

Stay tuned and follow our journey.

Surface-Area-To-Volume Ratio / Building Shape

Surface-Area-To-Volume Ratio / Building Shape

Surface-Area-To-Volume-Ratio

The surface area to volume ratio (S/V) is an important factor for the performance of a building. The greater the surface area, the greater the potential heat gain or loss through it. Consequently, a small S/V ratio implies minimum heat gain and heat loss. In order to minimise unwanted losses and gains through the fabric of a building, it’s desirable to design a compact shape, without articulation.

In theory, the most compact building would be a cube. This configuration may not be acceptable for many reasons, such as restrictions to daylight access, site and neighbouring character, planning regulations or simply personal preferences. However, to minimise heat transfer through the building envelope, the building shape and accordingly the floor plan itself, should be as compact as possible. With straight walls and first floor wall on top of ground floor walls. Deleting the need for additional roofing over nooks and grannies in the ground floor areas that stick out.

When designing your home consider thoughtfully what rooms are really needed. Instead of adding rooms you might need. Create multifunctional rooms, spaces that can be used for more than one function and that can easily adapt to a changing lifestyle.

Unfortunately this design principle isn’t supported by most council, as typically planners do not support straight walls without articulation or sheer double storey walls. We are currently working on a town house development in Kingston Council. In our original design we had all first floor walls sitting on top of the ground floor wall. In order to reduce wall and roof areas and hence to optimise energy efficiency. But regrettably, council forces us to step in the first floor walls. As they call it: to create more interest and articulation.

 

 

The Role of Ceiling Fans & Exhaust Fans

 

ceiling fans

Ventilation is the active process of “changing” or replacing air to regulate temperature and moisture. It should always occur under controlled conditions, by opening windows or with ceiling or exhaust fans, NOT through gaps and air-leakage.

Exhaust fans

Exhaust fans should always be self-closing, so that the replacement of air is controlled and not accidental. With out a self closing mechanism they are one of the main contributor of air leakage.

However, if they are self-closing they are an effective way to replace air, especially in rooms where no natural ventilation is available, or where natural ventilation might not be sufficient, such as kitchens or bathrooms.

Ceiling fans
Ceiling fans are an easy and cost effective way to improve the indoor air quality in summer and also to gain points towards the desired energy rating stars.

Ceiling fans provide additional air movement/wind, increasing the Relative Air Velocity (‘wind chill factor’) resulting in the apparent temperature felt on exposed skin to be 3 °C colder than the actual air temperature, thereby reducing the need for additional cooling.

Nowadays there are so many efficient fans available on the market.
If choosing a ceiling fan make sure you get one with at least 3 speeds, with the lowest speed being slow enough to still move air, but not to create a cool feeling draught, so that you can use them in winter mode)

 

Thermal Mass: material and colour selection

Material and colour selection

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Generally speaking, the more thermal mass the better and the heavier a material, the better its ability to store heat. The optimum would be a masonry home with a reverse brick veneer construction and concrete floors. Or using something like concrete block walls and insulate at the outside, with isolation boards.

If this option is too expensive use as much thermal mass as possible, concrete slab is preferable. In warmer climates the ground is colder and can help to cool the concrete. Therefore the indoor air temperature will be reduced. In colder climates, however, the concrete slab needs to be insulated from the ground in order to minimise heat loss in winter.  When looking a the energy start rating,  insulating the slab on ground can add up to 1 star to your star rating.

If a timber subfloor is requested or required, the focus should be at least on internal brick walls to the north which need to be exposed to the winter sun and are therefore able to absorb and release heat. Other materials that have a good thermal conductivity are water, sandstone, rammed earth and earth blocks, mud brick etc.

Moreover, colours and coverings can influence the performance of thermal mass. For example carpets and timber floors will minimise the ability of thermal mass to absorb and release heat as they work as additional insulation. This can lower the required heating in winter, but it will increase the need of additional cooling in summer, as the thermal mass can absorb less heat. On the other hand, hard floor finishes such as tiles, stone or slate on concrete slab can increase the ability to store heat. Dark colours or dark materials also tend to absorb more heat, however, light-coloured walls are more desirable as they maximise natural daylight. Dark walls will increase the need of artificial lighting, as they absorb light and can make rooms appear smaller. In short, material and colour selection can promote or adversely affect the performance of thermal mass.

One alternative to adding thermal mass as a actual building material is to add something that acts as thermal mass, but is light weight. There is one product on the Australian market, calle BioPCM. This phase change material acts as thermal mass, without the weight actual thermal mass has, and hence standard light weight construction and footings are sufficient, which are usually significantly cheaper than if you are building with brick and or block work.

“BioPCM™ is a lightweight smart thermal mass, providing design flexibility and easy installation for a cost effective and simple approach to integrating sustainable technology into buildings.
BioPCM™ absorbs excess heat during the day and releases this energy back in the evening as buildings cool.”

 

We have used the BioPCM to line the walls of a pantry, to keep it cooler and create some sort of cool – room. And the result was really great. The room always stays much colder then the rest of the well insulated weatherboard home.

 

 

Winter heat loss through Windows

Winter heat loss

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Unprotected glazing and single glazing in particular means the surface of the glass is noticeable colder than the warm air in the room. This lowers the room temperature and produces draughts. The Relative Air Velocity ends up too high and occupants will feel winter discomfort. For this reason, all windows require protection from heat loss in winter. To minimise winter heat loss, it is important to trap a layer of insulation still air between the window and the room. This can be achieved for instance by using internal coverings, such as drapes, Holland blinds, Roman blinds or Australian blinds, and thin or lace curtains combined with pelmets.

 Effect of window treatments on winter heat loss
(According to Sustainable Energy Authority Victoria 2002)

  • Unprotected single glazing: 100%
  • Vertical or venetian blinds: 100%
  • Unlined drapes or Holland blinds, no pelmet: 92%
  • Heavy, lined drapes, no pelmet: 87%
  • Unlined drapes or Holland blinds, pelmet: 79%
  • Standard double glazing: 67% (the higher the U-value the less the heat loss can be)
  • Heavy, lined drapes, pelmet: 63%
  • Double glazing with Low-E coating: 57%
  • Double glazing, heavy drapes, pelmet: 46%

Double glazing
The most effective way to protect windows against heat loss in winter is a combination of double glazing and internal window coverings. However, if internal coverings are inappropriate or not desired, for instance in highlight or clerestory windows, in kitchens or simply where unobstructed views are wanted, double glazing is an indispensable measurement in order to prevent heat loss in winter. Yet double glazing won’t prevent sun coming into the building, which means that the windows need to be protected from harsh summer sun by means of external shading.

Window frames
Another, often underestimated roll in the energy efficiency of a window, is the frame itself, as it can effect negatively on the overall performance. As we talked about in the blog “Adequate Insulation”, some materials, such as metal, glass or aluminium, allow heat to pass through them more easily, therefore they shouldn’t be used for windows frames if at all possible. If metal frames are used, such as aluminium, they should have thermal breaks to reduce the heat transfer. Generally speaking, PVC and timber frames perform better than metal frames.

 

Summer heat gain through Windows

heat transfer

It is important to protect windows with external shading devices, through appropriate window sizing and location, in order to minimise heat gain in summer.

Comparison of heat gains through different treatments for windows in summer

(According to Sustainable Energy Authority Victoria 2002)

  • Unshaded single-glazed window: 100%
  • Standard double glazing as available in Australia: 90%
  • Vertical blinds/open weave drapes: 76%
  • Internal venetian blinds: 55-85% (Effectiveness is reduced as the colour darkens)
  • Internal drapes or Holland blinds: 55-65%
  • Tinted glass: 46-65%
  • Solar control film/reflective glass: 20-60% (Available in different kind of configuration with varying effectiveness)
  • Trees, full shade: 20-60%
  • 1 metre eave over north wall: 30%
  • Roller shutters: 30%
  • External awnings: 25-30%
  • 2m pergola over north wall covered with deciduous vines or shade cloth: 20%
  • Outside metal blind or miniature louvers, parallel and close to window: 15-20%

External shading devices are an effective way to minimise heat gain through glass in summer and keep a building cool. They provide far better protection from heat gain than internal window covering. However, if external shading is not possible, internal coverings can at least reduce the unwanted heat gains. Shading devices should always enable ventilation outside the window, as shading fitted too closely to a window can trap warm air which can be conducted into the house.

Eaves, verandas or pergolas are commonly a part of the building structure, they are durable and do not require ongoing adjustments. It is essential to have a certain distance between the underside of the shading devise and the top of the window. But these fixed shading devises should only be used over north-facing windows, as they lack flexibility and aren’t adjustable. East and west-facing windows need a flexible shading devise that can be completely retracted in order to let the valuable sun through in winter, but to protect from the harsh summer sun. Adjustable shading includes amongst other things canvas blinds, different types of shutters, angled metal slats, louvers or shadecloth over pergolas. Adjustable shading requires action from the occupants, as they have to respond to climatic conditions.

Energy Efficient Window Design

window
The total radiation received per window varies according to the time of the year and the orientation. In summer, all windows receive heat gains, in particular those facing east and west. Whereas in winter, only windows facing north, north-west and north-east have a net heat gain, with heat gains outweighing heat losses. Windows facing all other directions will affectively lose more heat than they can gain. However, in the absence of northern solar access, windows to the east and west can provide some winter heat gains.
The most appropriate size of windows in terms of energy efficiency depends on many factors, such as glazing type, orientation of a building and thermal mass located inside the building materials. It is important to consider every room separately, as each room may have different acceptable limits and therefore may need different sized windows. Thinking about the windows early in the design process can save time and money otherwise needed later in the progress, to chase after the required stars to obtain a valid energy rating. We can help determine the effect of variations to window orientations, window sizes, internal glazing, double glazing versus single glazing, shading and internal coverings by using the FirstRate House Energy Rating software. Below are some clues on how and where to place windows.

How to orientate and size windows


Windows should be orientated to the north where possible. If solar access is good, north-facing windows should be large, but the size also depends on the amount of thermal mass in the building. South and east-facing windows should be kept pretty small, and windows to the south need to be positioned to enable cooling summer breezes to pass easily through the rooms. Whereas west-facing windows should be avoided where possible, if needed they should be relatively small and well shaded.
Appropriate window sizing, combined with double glazing, and/or close-fitting internal coverings such as drapes with pelmets, can minimise heat loss in winter. Furthermore, it is important not to overshadow windows in winter by the structure of the building itself, as it will reduce the solar access.


How to respond to poor solar access

Innovative design can overcome problems of poor solar access and overshadowing, especially in renovations, infill developments, higher density or small allotments with bad orientation, which can cause problems. In these cases, it’s important to use better performing insulation, protect windows, minimise overshadowing and courtyards, and reduce air leakage as much as possible. To compensate for poor solar access, the total window area of a building should be reduced.

Where solar access to north-facing windows is obstructed, clearstory windows are a good option to get solar energy into the building. Another option in responding to bad solar access is raising the sill height, as it will minimise permanent shaded glass areas, as these aren’t able to gain heat in winter and will lose heat instead.
Skylights and roof lights are also a good way to bring light into rooms, if obstructions from other buildings and structures prevent good solar access. Furthermore it’s a great opportunity to overcome overlooking into neighbouring properties, as windows above 1.7m don’t need to be screened. However, it is vital to protect the windows against harsh summer sun. Double glazing is mandatory as well as shading (a combination of external as well as internal shading would be the ideal solution).

Why Is Good Window Design So Important?

good window design

Windows are essential for a house and the comfort and well-being of its habitants, as they let natural light and fresh air into the building and enable views.

Appropriate window design, size, location and glazing treatment, combined with shading and internal covers, can significantly reduce the energy required for heating and cooling. Maximum solar access for north-facing windows can reduce winter heating bills up to 25%. External shading can block up to 80% of summer heat gain through windows. Double glazing and internal coverings can reduce heat loss in winter up to 40%.

Glass is the potential weak point of a building in terms of energy efficiency. A single glazed window can gain or lose up to ten times more heat than an insulated wall. The main heat gain through windows is due to thermal radiation. Windows receive direct solar radiation when the sun strikes the glass, but also diffuse radiation reflected from the sky and the ground. Between 30-40% of total radiation to north windows is diffuse, depending on the weather conditions. Radiation from the sun travels through glass to the inside of a house. This radiant heat is absorbed by thermal mass, building elements and furniture, which when warmed up, re-radiates heat to the room air. This re-radiated heat is trapped inside, resulting in convective heat build-up within the room. This process is called ‘glasshouse effect’. In order to hinder direct rays from the sun entering the building in summer, glass needs to be shaded appropriately. On the other hand it is also important to ensure valuable winter sun can shine into the house, as heat gains in winter can reduce the requirements for mechanical heating.

Read more about how to design and orientate your windows and the importance of avoiding thermal bridges in our other articles.

Apartment Renovation St Kilda – update

No matter how small or large a project, you have always to expect the unexpected. And no matter how well you detail and plan ahead, almost always there will be some complications or unexpected developments down the track, that will slow you down and will add to your well planned budget. Therefore it is imperative to always allow for some contingency within the budget as well as the time frame. And this is even more so the case when renovating. You never know what awaits you once you start pulling down walls, opening floors etc.

Even with this little straight forward renovation we had a few unfortunate setbacks, that did cost time and money. Originally it was planned just to replace the old dodgy power points with new ones. But when the kitchen was out the electrician advised us that the entire wiring was in a really bad condition, not up to current standards anymore and that he could not just install the power points as we wanted. We had to get the switchboard replaced as well as some of the wiring inside the walls. Which is a quite time intense and expensive job when working with massive brick walls throughout.

Also, once the old bath and the tiles came out we had to realize that the former plumber had done a really messy job, there where a lot of pipes where they didn’t belong and a lot more work involved then was anticipated.

Please check out the finished apartment under ‘Projects’

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view from living room into kitchen

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chalkboard wall in kitchen

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new shower in the making

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