How to Cool A Passive House In Spain

Well you’ve got three options. Break the rules and turn on the noisy fossil-fuel-burning electrical air conditioning and heat up the planet; incorporate passive cooling techniques into your design which frankly don’t work; or use a solar powered non electrical system which we install in our homes. Now I can hear you crying “hang-on he would say that wouldn’t he” so before I tell you about our system lets just have a look at the facts.

Cooling a passive house is a completely different problem to heating a passive house. We know the passive house technique works in cooler northern European countries. Seal the building and insulate it so no heat can escape and body heat and heat from cooking and appliances is enough to heat your home. Air quality is maintained with a mechanical ventilation system and heat exchanger (HRV). It can be minus 10 C outside before any artificial heat is needed inside.

What happens if we put the same building on a magic carpet and set it down in Andalusia Spain in August. Well it’s sealed and insulated so initially we are protected from the heat. But, big problem, we have to turn the HRV off because it’s hotter outside than it is inside. Soon we are breathing stale smelly air. And this is the big problem. If it’s hotter outside than you want it to be inside no amount of passive cooling techniques and clever designs are going to help you overcome this problem: stale air. You have no option other than to find a way of cooling the air in your building.

However there are some things you can and should be doing so let’s have a look at them.

Reduce Heat Gains in the Building

• Cook outside – not a bad idea we have a lot of barbeques in Spain. You could use an extractor fan in the kitchen.
• Use energy efficient lighting and natural light.
• People are a major heat source in passive houses so get rid of them (smile…I don’t think so)
• Look again at your domestic appliances, are they low in energy consumption and where are they located.

Design Your Building For A Hot Climate

• Shading : this is a vital part of a design in a hot climate. Shade to the south, obviously, but also to the west because the sun sets to the west and it is low in the sky making shading more difficult. Also the westerly sun is the afternoon sun and the thermal mass of your structure is more likely to have reached capacity. Shading includes overhangs, blinds, shutters and there are plenty of ingenious shutters that deal with the problem.
• Special Glazing: recent years has seen the development of window glass technology although it’s mainly for keeping heat in while still letting light through. You can install solar reflecting glass and solar absorbing glass and reduce your glazing to the south and west. This may compromise your enjoyment of the views and passive heating in winter so a balance needs to be struck.
• Thermal Mass: this is often the excuse for using vast quantities of concrete and is certainly why traditional stone buildings in Spain have such thick walls. Essentially you have bulky walls which absorb all the heat allowing you to stay cool inside. This method is entirely reliant on the bulk cooling down over night.

Make Yourself Feel More Comfortable

• Use cool colours: apparently psychologists propone this as a solution. I’m a psychologist and frankly I have my doubts.
• Move the air with fans.
• Use evaporation Techniques such as fountains and dripping walls which work well in dry climates but less well in humid climates.

Remember none of this is going to work in a hermetically sealed house if it is hotter outside than in because you won’t be able to use your HRV and the air quality inside will deteriorate to a point of being unsustainable.  You will have to open the windows and let all the fresh air, and the heat, in.

So How Do You Do It Then?

We install as standard in our buildings a revolutionary cooling system that uses the power of the sun to cool our buildings. Essentially this patented technology has achieved something which many thought was impossible: a “heat pump” with the unique ability to store energy and convert hot water to cooling and heating without the need for electricity. The same system, when installed, provides domestic hot water and heating in the winter.  We use an under floor distribution system so the very fabric of the house is at the right temperature, not just the air as is the case with electrical chillers and of course its silent and completely free to run.

This article was written by John Wolfendale a director of Eco Vida.