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Greening an Existing House – Part 1

Buy a house, or build a new one. This is a question that rattles around my head pretty often. What’s the most sustainable thing to do? This is the first post in a series on the decisions we’ve made in buying a house, part two will examine some of the things we want to do to Green our new house. I realized after I posted this, that I should have subtitled it…

Why buying an existing house can be greener than building a new one

Here are some options that I’ve thought through.

Build a New House

You could build a new super-efficient house made from all natural materials with no PVC or whatever you desire. I can envisage passive solar design, geothermal heating, a green roof and onsite stormwater and sewer treatment and reuse.

Unfortunately for most of us, this is truly beyond our reach, with money and local planning and health laws as the prohibitive items. Not just the planning laws, but also developer covenants over the land being purchased can be hindrances to good design, with colour, shape, size, materials, fencing and other requirements applied, often at the whim of the developer.

One of the biggest issues I have with the popular architecture market today is that rarely are they exhibiting or doing cutting edge sustainability with existing buildings, sure they are transforming warehouse spaces into funky urban living quarters, but what about something for the rest of us? That’s why I like the look of this book, Natural Remodeling for the Not-So_Green House, which is currently on my wish list!

Some of the biggest issues with new homes are with materials used. Read more after the jump…

Concrete, Steel and Timber

House Construction For every tonne of cement produced, approximately 0.9 tonnes of CO2 are released as a byproduct. If you are shocked to read this figure, it is actually an improvement on the previously high thermal requirements of the process and less efficient cementitous reactions.

Steel products are even worse on the greenhouse gas emissions by weight of product, weighing in at almost 3.3 tonnes of CO2 per tonne of steel produced.

Timber is a smart material to use in housing construction as it can be sourced from sustainable forests, is easy to work with and actually stores Green House Gases during its lifetime and milling process. Often the transportation of timber is less costly than of steel as many areas have some forests and milling within a 200 km radius, whereas steel production plants are usually very localized industries.

Here is a table from the NSW government comparing a timber framed house and a steel framed equivalent.

Source: Forest Facts: Forests, Timber and the Greenhouse Effect

The average floor area of a newly constructed house in NSW is 180 m2. In a timber-framed brick veneer house of this size, around 21 m3 (or a large truck load) of timber is used. In a steel-framed house, only 6.7 m3 of timber is used.

An average 180m2 house

  Timber Frame Steel Frame
Frame only 13 m3 wood 5 tonnes steel
Total house 21 m3 wood 6.7 m3 wood
Total carbon stored 9.7 tonnes 3.1 tonnes (in wood only)
Total carbon released to atmosphere in production 2.2 tonnes 6.0 tonnes
Balance of carbon 7.5 tonnes stored in structure 2.9 tonnes released to atmosphere

A steel-framed, brick veneer house on a concrete slab releases lots of carbon dioxide into the air, compared with a timber-framed, timber-clad house with a timber floor.

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The only issues with timber can be if the harvesting and replanting are not carried out in a sustainable manner. Forests are also a good option for GHG sequestration, and the harvesting of these products doesn’t cause leakage, rather it just stops collecting new GHG. However, new trees can be planted to replace the more mature trees. These newer plantings can quickly reach similar levels of sequestration as the existing trees. 

McMansions

If you are tempted by the size and colours of the modern McMansions on the tidy little culdesac in the neat new gated subdivision, consider the lifespan, sustainability and materials that you are buying into. Fittings, paint, plumbing, appliances are filled with petro chemical products, the least expensive materials can be used to create the largest house for your bucks. Passive Solar design barely rates a mention, neither does water or energy efficiency or air quality.

The Benefits

On the benefits side of building a new house there are a few.

  • New and Clean,
  • Construction and ten year warranty
  • Typically you can specify better insulation, better appliances etc.
  • Less up front maintenance.

These are all valid arguments for comfort and smart economic investing, but they don’t necessarily add up to sustainability. In the next article, I’ll consider some of the issues and benefits of buying an existing home, which is what we are going through right now as a family. 

 Again, here’s a link to what looks like a great book on remodeling an existing house.

 

Mike Thomas

Mike Thomas P.Eng. ENV SP, is the author of UrbanWorkbench.com and Director of Engineering at the City of Revelstoke in the Interior of British Columbia, Canada. If I post something here that you find helpful as you navigate the world of engineering, planning and building communities, that’s wonderful. But when push comes to shove: This is my personal blog. The views expressed on these pages are mine alone and not those of my employer.

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