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We want woolly walls

Why use wool when building? Well, it's a renewable resource, it’s healthy, low in conductivity, non-allergic, fire resistant, environmentally friendly, safe to handle, absorbs gases and fumes, and is low in embodied energy. And that's just for starters. In their latest blog, the First Light team explain why they think wool is pretty much the best ever insulation to use when building a house.  

One of the aims of the First Light project is to take the best of New Zealand and showcase it to the world. And in honour of that, we’re taking one of the country’s best exports to the world—in the walls of our bach, actually. We’re putting a woolly jumper over the house. How? The First Light house will be kept warm with wool insulation, a fact which perplexed a number of the US teams in the Solar Decathlon competition at a recent International Builders’ Show in Florida.   

The Solar Decathlon competition has 10 contests and the requirements of each have been considered in the planning elements of our house. The comfort zone contest requires that the house stay between a strict temperature range during the competition. This means the house needs to be incredibly well insulated. 

We looked at a number of insulation options before deciding to go with Kiwi company Eco Insulation. The entire envelope of the First Light house will be insulated by four layers of wool insulation from Eco Insulation. The layers will equal a minimum of 240mm of insulation which will give the house an R-value (used by the building and construction industry to measure thermal resistance) almost 3 times greater than building codes require in New Zealand. This may seem excessive but it will mean the First Light house is incredibly energy efficient and requires less energy to stay at a comfortable temperature, both during the competition and back here in New Zealand. 

When deciding which kind of insulation to go with, we factored in how the products were made as well as their sustainability credentials. Eco Wool is made from recycled wool which is sourced from carpet manufacture off cuts. They add polyester which bonds the product together. Using polyester means glues or resins, not overly environmentally friendly, aren’t needed. 

While the US teams may not be familiar with using wool in walls, wool has a number of unique qualities that make it ideal for our house. As well as being a local and renewable resource, it’s also healthy, low in conductivity, non-allergic, fire resistant, environmentally friendly, safe to handle, absorbs gases and fumes, and is low in embodied energy. One of the qualities which make it especially ideal for our house is that sheep wool insulation does not settle over time. This resistance to slumping is important in the First Light house as it has a very thick envelope compared to other insulation which could lose performance over time. 

The wool insulation has arrived and is sitting ready to be installed in our construction shed out in Lyall Bay. Now that the walls have arrived on site we are excited to get the insulation in and working. And come competition time, we’ll certainly be working hard to spread the word about wool as a safe, durable and healthy alternative.

Read more from the First Light team

A journey of miniature proportions

Take a 3D tour through First Light’s solar bach

Getting excited about solar design

Practice makes perfect

New Zealand natives in Washington DC

An actively passive house

What’s in a name? 

A team explosion (of size)

Showcasing Kiwi lifestyle to the world

How do you ship a house from Wellington to Washington?