Efficiency isn’t always sufficient

One of the problems of focusing on energy efficiency is that as buildings or products get larger, the impact is affected. Last week EiD had a related post. This week Susan Edmunds writes on the stuff.co.nz website about another example where the gains were cancelled. What is your experience?


Growing house size cancels out gains from better insulation

Energy efficiency was a priority in Hannah Blake’s newly built property.

When Hannah Blake signed up to start building her new home in Te Awamutu, the energy efficiency of the property was a key concern.

“We have an asthmatic child so ensuring the kids’ rooms were all toasty and warm, especially at night, was paramount.”

The 238 sq m house is fitted with more insulation that the building code requires, two heat pumps and a gas fireplace.

“Our house is fully insulated, toasty and warm. The house was built to capture the sun in the kids’ rooms in the afternoon. The builder was a genius.”

New research shows that while the Blake family might be comfortable in their new home, anyone assuming that their new house will be cheap to heat and comfortable to live in just because it is modern could be disappointed.

Hannah Blake’s new house was built to a standard higher than the building code.

Helen Viggers, of the University of Otago department of public health, has published a paper that shows the increasing size of new homes cancels out the effect of improved insulation and heating requirements.

In 1976, the average new house in New Zealand was 121 sq m. In 1996 it was 175 sq m and 2006 209 sq m. Now they are about 220 sq m.

“Standalone dwellings are increasing in size and are not required to be designed to take full advantage of the possible energy savings – for instance to make full use of passive solar energy,” she said.

EECA’s Christian Hoerning says people should really consider how big they need their houses to be.

“The increase in dwelling size in New Zealand has been sufficient to largely nullify the potential energy gains from increased insulation requirements of the last decades.”

Viggers’ paper said laypeople might not realise that a big new house could still be expensive to run. “Non-professionals will use the information with which they are presented, and if this includes a large dwelling size, and a stated high energy efficiency, many will not have the skills to know how to trade one off against the other. The information that a dwelling is built ‘to code’ may appear initially to be synonymous with it being a low energy building.”

She said the building code should be stricter because it was easier to build new homes to a high standard than it was to retrofit more insulation later on.

People buying new houses off the plan should ask the developer for better quality insulation and more of it, she said. “People are building to as poor a quality as can be legal.”

Viggers said people worried about the cost of a higher standard but, if it was required of all new builds, economies of scale would help make it more affordable. People would save money in the long run, she said.

EECA Energywise technical expert Christian Hoerning said it was worth people thinking about how big they needed their houses to be.

“Think about how much space you need on a day-to-day basis. Smaller houses are cheaper to build, easier to heat and use a lot less energy,” he said.

“Building a smaller house may also mean you can afford higher quality energy efficiency products and features. As demonstrated by the research paper, there is a lot of scope for exceeding the minimum energy efficiency requirements of the building code by applying best practice energy efficient construction methods and products.”

That could include higher levels of insulation, double-glazed windows with insulation frames and low-e glass, energy efficient lighting, space and water heating or a heat recovery ventilation system, he said.

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out /  Change )

Twitter picture

You are commenting using your Twitter account. Log Out /  Change )

Facebook photo

You are commenting using your Facebook account. Log Out /  Change )

Connecting to %s

This site uses Akismet to reduce spam. Learn how your comment data is processed.