10 Tips On Building Green Homes

10 Tips on building green homes

Below is a list of tips on building green homes based on my experiences as an environmental designer, working with green orientated clients, regular questions I get asked from people, and mistakes I see happening in the construction industry.

What makes an eco, green, environmental or sustainable home is varied as much as it is specific to each person, organisation or company. The under laying principles are that the home will use less resources, is healthy and comfortable to live in, reduces negative impacts on the environment throughout its life cycle, and reduces the amount of climate change we individually contribute too through our living habits.

The reality is, building homes is the worst act we can commit against the environment given the amount of intense consumption of natural resources required for construction, industrial produced materials and technologies , and overall life time resources required to run the home. So, if we are going to build, its makes allot of sense we get it right , rather than building an expensive, resource hungry home that eats up more than it gives back. There is no reason why every home in New Zealand couldn’t be environmentally designed to harness sunlight for natural warmth and natural air flow for cooling, these two factors could cut the nations power consumption for houses by one third while significantly improving occupants health through the minimisation of condensation, mould and dampness.

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Tip 1. Understand your site. Each site is unique in its own right and has a different set of environmental conditions that need to considered before we start designing. These are some of the questions we should ask about the site. What are the local seasonal sun path directions? Where does the sun rise? Where does it set? Where will it be in mid-June when you need it the most? How do the prevailing wind directions impact on the home? Is the home going to receive the cold south west winter winds? What other unique micro-climates impact on the home? Will parts of the home be in shade due to a hill or large trees?

Tip 2. Get the floor plan layout right.Each site is different, each person is different, and therefore every floor plan should be different. Tailor the home to work with your living habits, make it work for view or outlook onto a courtyard if possible, give priority to maximisation of northern aspect for solar gain (each room should get 2-3 hours of sunlight per day), living spaces should be given priority to sunlight followed by the bedrooms. The function of the home should be governed by the function of the surrounding site. Not the other way around.

Tip 3.Build smart and educate yourself on cost. Find out what the real cost of building is for your unique requirements and work backwards to the architectural design, small, medium and large budgets. Its better to build an intelligent home which you can afford, be happy to live in and can sell for more latter, rather than building a big house thats not well designed, uncomfortable to live in, expensive to run and wont sell for much more than what you paid for it. Smart green homes can be any budget and any type of design e.g. a brick and tile house, earth house, colonial style, modern style. So be realistic with your expectations and make the budget work for your requirements.

Tip 4. Energy efficiency, invest in insulation. Keep in mind the New Zealand building code is the minimum standard we are required to build too. Its not the maximum bench mark we should be aiming for. What this means is, increase your thermal R value rating for walls, ceilings, and floors as much as possible, relative to your location and budget requirements. This will significantly save on heating costs over the life cycle of the house. Insulate the concrete slab and think about the thermal envelope of your home. The thermal envelope is like a blanket which wraps around your home and keeps heat inside. Any part of the home which is not insulated is going to loose heat. All windows should be minimum double glazed, ideally with a thermal drape or thick curtains to keep heat inside the home at night.

Tip 5. Passive solar gain and thermal mass. Passive solar gain uses what is already provided to us by nature. This is abundant free radiant energy from the sun, which New Zealand has plenty of. Correctly designing for sunlight reduces dependency on mechanical devices for heating or can eliminate these altogether. Insulated thermal mass or concrete is like a re-chargeable battery that uses sunlight instead of electricity for heating. During the day time sunlight is beamed onto the floor, this energy is then absorbed by the concrete and retained with the help of insulation. When external temperatures begin to cool during the evening, heat is then released (or conducted) from the slab. Concrete slabs are also able to retain and release energy for many days without regular sunny days when designed correctly.

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Tip 6. Passive ventilation and stack effect.Cross ventilation is the most straight forward form of natural cooling available to us. This entails understanding what direction the seasonal winds will come from and allowing for the maximisation of this air flow through the home, mainly during summer. Stack Affect works on the principle that external cool air is always on the ground level and will be pulled into a home as warm air heats, rises and exits. This in turn creates a continuous movement of natural ventilation with constant cycles of fresh air entering and exiting the house. The motion can be likened to a set of lungs which breathe for the home providing fresh air to the occupants.

Tip 7. Passivhaus design. Passivhaus design originated from Germany and has gained good momentum over the world (mainly in cold temperate climate regions). Achieving the Passivhaus standard is reliant on a very high-performance building envelope and computer analysed site-specific weather data, resulting in low energy use. How relative Passivhaus is to NZ is still being debated. In compromised site situations which dont have consistent exposure to sunlight the design strategy makes allot of sense. Passivhaus was developed in a colder country where for example sunshine hours in Germany, Berlin are approximately 1700 annually, compared to Auckland which has approximately 2100 sunshine hours annually. The amount a direct exposure to the sunlight has a significant impact on how we design, materials we use and overall building costs.

Tip 8. Green materials and Cradle to Cradle thinking. Cradle to Cradle is a circular process in how we perceive and think about green materials. These are some of the questions we should ask about materials. What is the material? Where does the material come from? How is the material made and from what? How will the material perform its function in the home and for how many years? Where does the material go once we have finished with it? What is the materials second life-cycle? There are also many green certified materials, each certifier has a different criteria they are looking for and award ratings based on this. Its probably a good idea to do a quick search online and see if your principles fit with that of the certifier.

Tip 9. Green Technology. The purpose of all technology it to simplify, economise and improve our lives right? Then why does it feel like such an awkward burden with so much reliance placed on technology to save the day. Short answer is, we live in heavily consumer driven based society where everyone wants to sell you something, even the green technology companies. The trick with all green technology like solar, wind, smart insulation, energy efficient appliances and green gadgets etc. is to design homes which intuitively engage with the natural environment, rather than resisting it. This is achieved by unlocking natural resources like sun, water, wind and air flow through correct environmental design. This reduces dependency on smart green technologies. Typically what happens is the environmental design component is poorly considered from the start and we rely on smart green technologies to save the day. A 240 square metre smart energy efficient passive solar home which is well insulated and designed correctly might use 3000 kWh annually (electrical energy), instead of the national average of 8500 kWh annually. This means less dependency on all technologies across the board.

Tip 10. Engage design professionals. The reality is, most New Zealanders will try and save a buck where they can, which typically means cutting out the design professional and moving directly to construction. This makes little sense if youre investing your life savings into a poorly designed home and even worse sense for the environment. We have to value and use all resources as preciously as possible. Unfortunately this is not how the consumer markets are structured these days and you need to be weary of this.

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I think all we have to do is look around at whats being built (not to point the finger- but volume house builders are a classic), the uncomfortable nature of living in many of these homes and expensive power bills we are burdened with. So, what to do about it? Change our attitudes. Whatever money you invest into design is added value into the project. A well designed house is going to sell for more (probably much more than the additional design fee factor), will sell quicker (less stress if youre keen to move on), will make you happier and is better for your physical health. Work out your realistic budget and ask a design professional for a proposal, even if its only a concept design.

Building a home is probably one the hardest and most creative, fulfilling life journeys we can make. If we do it well it requires an open mind, determination, patience and persistence, the end results make everything truly worth it. I wish you all the best with your building journey.

Duncan Firth is the founder of Solarei, an architecture firm combining environmental design with modern architectural form.


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