Environmental house design

Green Building, Environmental design, Sustainable Architecture

The terms “green building”, “environmental design” and “sustainable architecture” are just a few of the terms that are used when describing a home that is designed to minimise it’s impact on the natural environment. In this article we use the term “environmental design”.

When designing a house to be environmentally friendly, it is important to rememeber that good environmental design will positively effect the thermal comfort of a building allowing the occupants
to be comfortably warm in winter and surprisingly cool in summer. It will also result in minimal energy usage.

There are 6 main areas that need to be considered when planning your new home or renovation and bearing the environmental design in mind. The information given in this article applies to sites at a latitude of approximately 32° but a lot of points may also be applicable to wherever your home is located.

Environment Design

Ideally the site you purchase ahould be flat and have its backyard facing north towards your view. This will make designing an environmentally friendly house much easier.

Sun Penetration and orientation

It is very important that you spend a good amount of time assessing direct sun penetration onto your site before you start designing your home.  If it were practical, and you oriented all the internal spaces in your home to north, it would be relatively straightforward to build a home that was thermally comfortable all year round. However in the non-ideal “real-world” this is rarely possible. A great book to use when planning around sun and shade for you building is “Sunshine and Shade“, written by R. O. Philips of the CSIRO. Use the basic rules listed in this book to aid you when planning the various spaces in your home.

Controlling the amount of Sun

There are many methods of controlling the amount of sun penetration in your home helping a house stay cool in summer and warm in winter.

Roof overhangs: If your home is located in a very sunny climate and will be drenched in full sun, ensure that all windows have a standard window and door shading depth of 900mm.  600mm is the normal project home depth but this is probably not enough.  This depth can be slightly altered depending on the orientation of the external walls to north.

Other control devices: If you have no choice in how you orient your living areas, and are forced, for example, to orient them towards the direction with the harshest exposure, you will need to get creative. One solution is to plant deciduous trees about ten metres from your house.  This will block hot afternoon summer sun and allow winter afternoon sun to penetrate through to your home. If this is not an option due to views or council regulations, the best solution is an operable (adjustable) window device like an awning or louvre system.

Room orientation

If you have shading on your site you need to think about the room type and design to get the optimum sun penetration into the space; e.g., locate laundries, bathrooms and storerooms to the west or south.  These rooms can be physically cut off to control the hot sun or the cold resulting from a southern facing orientation. Bedrooms work best located on the side with the most morning sunlight however this may not be the right way to go if you have to consider shift workers.

Thermal massing

There are currently a wide range of building claddings that have naturally occurring thermal benefits. Products such as core filled concrete block work, double brick, mud brick or hay bales offer internal spaces warmth in winter and coolness in summer due to the thickness of the product and the time it takes for heat of cold to penetrate these products.`Core filled block work, double brick, mud brick and sandstone, for example, have the ability to draw the relatively constant temperature of the ground through a building.

Insulation

Wall and ceiling insulation will have a hude impact on the cost of heating and cooling your new home. All cladding types have an R-value, the higher the R-value the longer it will take for the outside temperature to enter you home.

Many houses today are timber framed and without any extra insulation these homes will not be hot and cold in the wrong seasons but it will also rate poorly with BASIX (BASIX is the Building Sustainability Index.).  There are too many products to name, but insulation generally come in the form of “batts”, air cell blankets (like bubble wrap), loose pulp, and “sheets”.  Heat is lost primarily through the ceiling of a home, then the walls and windows, and lastly the floors.  If your site faces a windy direction, and is located at the top of a hill, your floors will also need to be insulated.

Sarking is a reflective fabric that reflects heat away from the roof and external walls and it should be laid with the reflective side facing outwards.  Roof sarking often forms part of an insulative blanket that is laid on top of the roof trusses and under the roof battens.

There are many new products on the market that are a “sandwich” format product (cladding on one side, a finished lining on the other, and insulation in the centre).

Windows and doors

If your house has been designed using the items suggested in this article, and your windows and doors are not too large, you will not require anything more than standard single glazing throughout your home.  Glazed windows and doors are both referred to as windows in the glazing industry. Below is a list of a few basic types that you need to be aware of:

The size and location of your windows are also very important.

Use the following general rules to reduce winter heat escape and summer sun penetration:

Sub-floor construction

The space under your house is call a sub-floor and correct subfloor construction is very important in keeping energy costs down in your house.

Don’t allow air to flow too freely under your house as this increases your energy requirements for heating and cool.  If the building is sitting on brick piers ensure that sub-floor perimeter is clad: the better clad this area is, the lower the energy requirements.

A concrete slab that is laid directly on ground is the most energy efficient subfloor because the slab draws on the relatively constant temperature of the ground and radiates that temperature into the house.

Colors

House colors and temperatures work much like colored clothing.
A dark brown T-shirt attracts heat and is much hotter on a summer day than a white T-shirt, and your house is exactly the same, especially the roof.
If you choose a light colored roof you will get a better energy score as a light colored roof reflects the heat better.

The shape of your roof will greatly help you control the temperature of internal spaces within your home and where possible have large roof cavities that a truss can provide.

Where a skillion or flat roof is unavoidable insulate with R5 insulation.

Many new homes don’t have roof ventilation.  Roof vents remove excess heat from the roof space preventing hot air in the roof radiating through the ceiling.  Roof venting will also reduce mechanical cooling and heating requirements.

Wastage

Whenever possible you should always think about wastage of building materials.  Many designers work to 600 and 900mm increments in room sizes etc as most building materials are manufactured in increments of these.

Any wastage during construction can be used on site especially concrete and bricks, these can be used for fill.

If you are demolishing a building the windows and doors can be sent to a recycle yard as can timber framing and flooring and various fittings.  Any concrete, tiles, masonry or brick can be recycling for future use as road base, there are companies that will take the materials for free and you save on expensive tip fees and reduced land fill.

Energy efficiency

When you are in the throws of construction and you are handing out money everywhere it is difficult to allow extra money for the long term energy efficient items.

Lighting

It always happens, the home is almost completed and the budget has been blown, the last things to be fitted are the electrical appliances and fittings… how unfortunate. So quite often the cheapest fittings are chosen, but unfortunately they are also the least energy efficient.  Spend the extra money at this time and invest in future energy savings. Related reading: Energy Efficient Lighting

Hot water systems

The energy required to heat a regular electric hot water system accounts for 60% of the total household energy requirements.  Hot water systems vary greatly in efficiency, price and capacity but generally a gas-boosted solar system is the most energy efficient hot water system. Try to install the right size hot water system for your family to ensure you reduce energy costs.

Household Appliances

Energy efficient appliances also seem to be more expense when initially purchased.  But before you go down that path do some research and learn more about how to choose your energy efficient appliance, and save money over the long term.

Curtains and window dressings

Any kind of curtain or window dressing that provides a good air pocket between internal spaces and your window will definitely save you energy.  Blinds may look better in certain situations and reduce power bills a little, but be aware that blinds do not offer the same ability to cover a window as curtains. Timber and venetian blinds help very little towards saving energy.

Embodied energy

Embodied energy is the energy used to produce a product from beginning to end. In this section of this article we examine the embodied energy of common building materials.

Take a look at the list below which outlines the embodied energy measured in kiloWatt-hours (kWh) per tonne that is required to manufacture common building products, from least efficient to most efficient.  Also see  www.sustainablehomes.co.uk

So as a general rule remember that natural building products require less energy to produced than man made products, and use recycled products where possible.  Embodied energy is a huge subject but it is an aspect of the energy efficient building process that is missed by many designers. Keep in mind that one of the most energy intensive products to use in construction is concrete, and the most economical is timber, so use plantation timber every chance you get.

Water efficiency

Rainwater and storm water tanks

If you live in a climate where water-shortage can be a problem, then you might want to consider installing a rainwater tank. There are now non-obtrusive underground, sub-floor bladder and in-slab options if you would prefer something less invasive than a hude water tank in your garden..

There are many fittings that comply with the minimum 3A compliance requirement for wet area fittings, there are even 5A rated products.

Eco friendly materials and pollution

This is where many energy efficient and sustainable products come unstuck.  The by-products created as a result of manufacturing building products are often toxic and these products can release harmful chemicals during their life time.

Some examples are arsenic in treated pine, mercury in compact fluorescent bulbs, and various toxic by-products from PVC.  For more information on toxic building products see:

Conclusion

In short, designing and building an environmentally friendly home can be a tricky and challenging task.  A great deal of research needs to be done, but for many people it is worth the effort to ensure that your family is living in a non-toxic, energy efficient and healthy home. In the long term, the effort and patience will also pay off with huge energy savings and will have a huge impact in reducing your carbon footprint.

Further reading