|40,000 NZ home owners were right all along. Many people who have lived in solid wood houses comment on how warm and comfortable they are. This is in spite of these houses having walls with a low R value. A group of companies wanting to promote solid wood buildings asked Dr Larry Bellamy of University of Canterbury and Don Mackenzie from Lincoln University to research why these houses performed better than their R values indicated. The results of this work was quite a surprise to the researchers , but probably no surprise to the 40,000 families living in solid wood houses in New Zealand.
The first thing they found was that solid wood has significant thermal mass giving it the ability to store the sun’s heat during the day and releasing it at night. Brick and concrete are often used because they provide useful thermal mass but wood has up to 2.5 times as much thermal mass as concrete per kilo. Dr Bellamy was able to use a building simulation model from Denmark to show that when this thermal mass effect was added to the relatively low R value of the external walls, a solid wood house compares very well to a light timber frame house built to the NZ building code. The solid wood house performed even better when solid wood internal walls and ceilings were used.
Probably an even more important discovery was the effect solid wood walls have on the health of people living or working in such a building. It has become well known among researchers that relative humidity in buildings needs to be kept between 30% and 55% to avoid the build up of bacteria, viruses, fungi and mites, and to minimize respiratory infections and asthma. Dr. Bellamy found some research from the Fraunhofer Institute, near Munich in Germany, which compared 2 identical rooms. One had walls lined with solid wood and the other with painted plaster board. Water vapor was added at different times of the day to simulate people living in the rooms.
The solid wood lined room was found to have a remarkable ability to moderate over 50% of the moisture variations so that the room was only outside the safe humidity zone for 3% of the time compared to 27% of the time for the room with the painted plaster linings. This research from Germany indicated that the health benefits of living in a solid wood house are likely to be even greater than just the thermal comfort.
Many of us have become aware of the benefits of wearing merino, especially for strenuous outdoor activities. The merino is able to work naturally with the body to store and release moisture and stabilize body temperature. Merino also has the ability to reduce the build up of unpleasant odor. Wearing merino and living in solid wood houses both help keep the body healthy and active.
Can you destroy a solid wood building?
Solid wood buildings have withstood severe storms and earthquakes when nearby buildings have suffered catastrophic failure. Notable examples are Cyclone Tracy in Darwin Australia and the Edgecombe earthquake in New Zealand.
Solid wood walls can take the hard knocks when used in kindergartens or motels and can have minimal maintenance costs compared to painted plaster walls. Solid wood even performs well in a fire and can be restored after a minor fire.
Solid wood’s ability to moderate humidity and to breathe means that it can survive, in a wide range of climates, probably for hundreds of years. If it needs to be moved, it can be moved as a whole house, or dismantled and rebuilt on a new site.
Tackling Climate Change with Solid Wood Building
While there is still uncertainty about the best way for New Zealand to tackle climate change and meet Kyoto commitments, growing trees to store carbon is likely to be the most cost effective way. A farmer can plant a low value steep piece of land and store over 20 tonnes of CO2 per hectare per year for the next 30 to 50 years. When the trees are ready to harvest, if the wood is used for a solid wood building, it can keep that carbon stored for maybe hundreds of years. It also saves the use of energy intensive materials such as concrete, steel and brick. And because solid wood buildings are easy to keep warm, more energy can be saved. Solid wood building saves considerable amounts of precious fossil fuel energy compared to other building systems, as well as storing significant amounts of carbon over the life of the building.