Air, what is it?

The air we breathe sustains life, but it also comes with other things!

Oxygen, nitrogen, plus other smaller amounts of other gases plus water vapour and particulates (dirt) are all being carried by the air. Air also has mass which means it can accept, store and release energy.

What are we trying to do?

This is the question we need to ask for each part of any project. In this case, we have the three key elements to consider.

Taking a winter’s walk provides the answer. Out on a crisp winter’s day with our woolly jumper to keep the cold out and a breeze turns into a wind, we get the wind-cheater jacket out before the cold wind can get through the wool and chill us.

As the walk continues we get warmer and maybe too warm, so we unzip the jacket a bit to prevent sweating. Later, we get to a field and there is a bull looking at us, but a cafe for a drink beckons.

Can’t go through the field, so we go around it!

The three key elements:

1. Insulation – woolly jumper

2. Air barrier – windcheater jacket

3. Ventilation – opening the jacket

We could also include control because adjusting the amount we unzip the jacket is control.

Air flow is the key to lower energy use.

Air can move a significant amount of energy, and we have two air flows in every building. We have wanted air flow, which is the supply of fresh filtered air that provides oxygen for us and any animals or plants.

We also need air for the combustion process in open fires or other heating equipment that needs a separate air supply as well as need to remove moist stale air to keep the building.

Then we have unwanted air flow which enters into our buildings, because we may leave a window or door open which affects the comfort and we close the offending door or window.

But mostly it comes from the unseen gaps, cracks and holes left during the construction of our buildings.

Air will travel through these gaps and cracks left during the build process and enter the home if not sealed correctly.

Locating leaks themselves isn’t expensive, but it is crucial, because if the home has many air leaks it takes more time to heat the house, using more energy and therefore increasing your bills.

Airtightness is important. This is about preventing air flow through a building to conserve energy. In a new building 50% of the energy used to keep warm is used in replacing the energy lost to the unwanted air flow through a building.

Preventing unwanted air flowing into or out of your home WILL save on heating costs. In older existing buildings much more air flow is evident over five times more!

Barriers are the best way to deal with this. When air flows through insulation it takes energy with it, while any air flow around insulation can remove energy as well.

Remember the bull in the field we avoided by going around, air finds the easy path around insulation if it can’t get through.

Any gaps in your insulation reduce its performance, and become the easy pathway (or thermal bridge) as the energy tries to avoid the barrier. Any voids (hollows) allow convection currents to increase energy transfer considerably.

Ventilation is also key. A building that has no ventilation will suffer from condensation problems, so we need to exchange moist stale air for fresh air. But we don’t need vast amounts of fresh air.

Too much unwanted air will increase your heating costs.

Needing to remove this air with just an extractor fan means throwing expensive energy within the air away. Using extractor fans also pulls in outside air from those gaps around the building!

We need to recover or reclaim the energy is this air flow and use it inside the building to heat the fresh air or provide hot water; thus saving money.

Next month we deal with air leakage in a building.