Air quality is determined by the composition of the volume of air under consideration. Generally, the normal composition of air is 78% nitrogen, 20.95% oxygen, 0.93% argon, 0.04% carbon dioxide, trace amounts of other gases, and around 1% water vapour. Substances not naturally found in the air or found in the air at higher than usual concentrations are pollutants which are detrimental to air quality.

In healthy house terms, we are interested in indoor air quality; a lack of ventilation can concentrate indoor air pollution and our living patterns bring about prolonged exposure to pollution. So what pollutants are we at risk from?

Radon is a gas that in certain regions (especially those where granite bedrock predominates), emanates naturally from the Earth. It is a carcinogen, wherein the risk to health lies. Researchers have estimated that radon in the home causes approximately 20,000 lung cancer deaths in the European Union each year, around about 1,000 of those in the UK. [Ref: BBC News]
As it exudes from the ground it can become trapped inside the sealed envelope of a building and increase in concentration. Where there is a significant risk from radon emissions, the risk is usually mitigated through the employment of a radon barrier as part of the floor construction.

Formaldehyde (the stuff used in embalming), which is toxic to humans in high concentrations, can be emitted from building materials such as plywood and foam insulations and furnishings such as carpeting. Minimising the use of such materials will mitigate the risk.

Volatile Organic Compounds (VOCs) can be introduced through selection of certain products. Within and around the home, common artificial sources of VOCs include paint thinners, dry cleaning solvents, wood preservatives and petroleum fuels. The nature of the risk varies inline with the exact compound; they are variously carcinogenic or causative of respiratory problems. It is also important to note that VOCs are a significant outdoor air pollutant and contribute to global warming.

Although no longer produced, the lead in lead based paints can degenerate into dust and be inhaled. Lead is poisonous and can cause damage nerve connections.

Air pollution can also be introduced intentionally, the use of air fresheners, burnt incense, scented cleaning items all add foreign bodies to the air breathed within the home. Similarly, open fires, wood-burning stoves and other non-sealed carbon fuelled heat sources can smoke particulates to the air, both inside and out.

Also related to carbon fuelled heating systems, carbon monoxide is a colourless, odourless and lethal gas, poisoning from which is often caused by faulty ventilation and chimneys.

A further concept of interest is that of Indoor Surface Pollution (ISP). ISP is defined by reference to the Fleece Factor – the area of the building that is carpeted, curtained and in other ways clothed with fabric and the Shelf Factor – the area of open shelving or other storage in the building. By consideration of these, in relation to the people and pets that reside within the space and the nature and frequency of cleaning we can begin to gain an appreciation of the nature and quantity of air-borne microscopic particles, potential effects of these and methods for minimising them.

Many of these pollutants can be introduced during construction of the building; therefore, we should allow a new build to air out for a period of perhaps 2-4 weeks prior to occupation.

The reduction of air pollutants and associated quality of the air are factors over which we have control through the choices made when designing, building, maintaining and living in our homes.

It is only over the last few months that I’ve become aware of the concept of the healthy house. This is a design approach that focuses on the effects upon human health of the design, materials, building alignment & layout of our built environment.

In the best tradition of ‘Top-10 lists’, here’s my ten key considerations of healthy house design. Each is accompanied by some basic notes; with more detail given in the posts that each heading links to.

Air Quality
Whilst modern insulation pushes us toward living in an air-tight cocoon, our needs for clean & fresh air push us in the other direction.

Allergy Free
With allergies becoming a modern epidemic we need to ensure the materials we employ do not exasperate an already harmful situation.

Colour
We are only beginning to understand the effect that the colours that surround us have on our moods and motivations.

Cooling
Too-hot / too-cold ~ cooled in the Summer / heated in the Winter.

ElectroPollution
Another aspect of our environment we are only now starting to understand is the impact on us of the electro-magnetic fields that we weave around ourselves with electrical goods and metals.

Heating
If we use radiant heat, that warms us like the sun, do we gain the added vitality of a warm sunny day? Do traditional hot water, radiator systems drain and tire us?

Light
Natural or artificial & the impact it has on us from dawn until dusk.

Mould
Humidity levels contribute to mould growth; modern bathing habits contribute to humidity…mould spoors cause asthma, therefore, control mould.

Size, space and proportions
From basic considerations such as the practicalities of room sizes to sacred geometry.

Sound
Not only is silence golden, but sound can tie us to our surroundings, sooth us or excite us. But no-one likes the constant drone of traffic as the theme tune of their life.

These are what I feel are the 10 key design drivers we need to consider when designing our home in a healthy and to some degree sustainable, ecological & environmentally sensitive manner. If you don’t agree or have something to add them please add your comments.

There’s been some pay-back from the bramble clearing that we spent so many weekends doing.

Nettles! …and where there are nettles there’s soup.

Get over to mwnch ~ eat seasonally for the recipe and get cooking.

When working through the detailed design for the barn we decided to use oak beams to support the first floor rather than steels. That seems like a sensible decision; whilst costing more, from the perspective of aesthetics and ‘healthy house’ design the choice was clear.

Now I’m trying to set the budget, the madness begins. I’ve had two prices – one from a website and one from a national timber products (floors, doors …) supplier with shops across the country & glossy ads in all the self-build maqazines. The two prices vary by a factor of 10.

Whilst one is an installed price and the other an out-of-the-factory-door-undelivered price, that’s still one heck of a variance and one that makes me question the choice we’ve made.

[EDIT: After double checking figures and canvasing opinion: whilst both prices still stand, the lower and more acceptable one appears achievable and so the wood stays!]

From the Romans to present day, underfloor heating has been a good idea. Underfloor heating provides gently radiating heat from the whole of the floor surface. This radiant heat is similar to the heat from the sun, heating the occupants of the room directly rather than the air around them (must admit I’ve never fully followed that, but that’s what I’m told!). As such the whole of the room is heated and the hot / cool spots and convection air currents caused by traditional radiators avoided. Thus dust movement is reduced and humidity levels in the air maintained – the moted health benefits for underfloor heating lie in these attributes.

Is it green? Underfloor heating has a couple of green credentials:

• It requires a lower water temperature (and therefore consumes less energy) than traditional radiators.
• Heat wastage is minimised as the air is not dried-out or circulated unnecessarily.

The underfloor heating pipes can be set into the screed of a structural floor slab or laid on-top of the floor slab in a layer beneath the floor covering. Maintenance of the pipe work is minimal once installed and should last as long as the floor it is set into.

Running costs are attractive at up to 25% less than a traditional radiator based system running off the same heat source. Additionally, installation costs are comparable.

Many heat sources can be used in conjunction with underfloor heating. Perhaps the current system of choice is a ground source heat pump … of which more coming soon …