Building Biology covers the interrelationships between humans and the built environment and attempts to improve our built ecology. This is both our impact on the external environment, but also how the internal environment, that we’ve created, affects our health.
Building Biology is a design mindset rather than an Ecolabel (like the U.S. WELL Building Standard for example), which is fundamentally linked to carbon and energy saving. The SBM 2015 guidelines are a three-page document of measurable targets that can be used to identify risks and target improvements tailored to the building type, venerability of its occupants and what’s achievable within the budget.
Sleep is fundamental to our mental and physical health, so the SBM 2015 concentrates on improvements to sleep areas. It looks to design around perceived and known risks in buildings or areas of a building where people inhabit for extended periods of time. It assesses the dose as well as the exposure and is therefore ideal for dwellings.
Natural and Mechanical Ventilation
Relative humidity has a large bearing on dust. Greater than 60% humidity allows bacteria, viruses, mites and asthma to become more prevalent; below 40% humidity and respiratory infections, ozone and asthma also begin to rise. Additionally, below 40% humidity, electrostatic charge becomes more active/dominant in the movement and transportation of dust particles.
Ventilation is key in the control of humidity and temperature. Dwellings typically need between 0.6-1.0 air change per hour (ACH). Natural ventilation alone is not sufficient, so the optimum solution is constant background mechanical ventilation with heat recovery (MVHR) with good cross ventilation purging capability in each room for short rapid ventilation when needed. In our experience cross ventilation is most effective where windows are located on opposite and/or adjacent walls, rooflights and north lights are helpful but not as effective. Note: at 1.0 ACH you need to be careful in winter not to reduce the relative humidity too much.
Within the MVHR system, the heat recovery device should not be a “thermal wheel” as between 3-5% re-circulation and mixing of contaminated air can be evident over time. In addition, the use of earth ducting systems pre-heating and pre-cooling incoming air is discouraged due to risks of poor installation practice and build-up of moisture and mould in the below ground pipework, which is then very difficult to correct once installed.
Water, Hot Water and Heating
UK mains water quality is overall very good and is covered under EU regulation (98/83/EC). Whereas, bottled water is covered under the food regulations which are less stringent (except for one area which relates to nitrate levels). Our mains water can contain significant nitrate levels due to run-off from farm land. Filtering of mains water does not need to be considered unless nitrate levels are high as nitrates react with copper. Copper pipework and heavy metal deposits are not good for the human liver.
The best course of action is to design your potable kitchen tap connection to be the nearest fitting to the incoming supply and serve with stainless steel pipework. In this way there are no drinking water dead legs, and water with PH>7 or high nitrate content has no adverse effect. Based on this practice, installers should be aware of galvanic corrosion, so opt for plastic PE or PP pipework for the remainder of the house.
Note: We find plumbers like to balance the hot and cold-water services from the domestic hot water cylinder, meaning that the potable connection is not the shortest. This is counter intuitive to Building Biology so this needs to be designed correctly.
Building Biology takes a similar approach to Passivhaus in terms of passive improvement, and comfort, where no surface is more than 40C higher or lower than the air temperature. This also places a focus on the use and incorporation of thermal mass to regulate temperature and humidity swings, but we’ll touch on this further in the Building Fabric Blog next time.
What heating remains should be delivered via a low temperature radiant system (http://www.healthyheating.com/). Building Biology believe in this delivery both in terms of comfort and the human response to radiant heat, but also to reduce/eliminate convections cycles which will minimise dust movement. These systems can be in the form of low temperature underfloor or wall heating or even skirting board heaters. (http://www.discreteheat.com/thermaskirt/products-and-information/how-does-it-work.aspx)
Once heating requirement has been satisfied, hot water becomes the major focus in the UK. Most developments should opt for solar thermal panels feeding into a thermal store. Typically providing annual coverage of between 2000-3000L should be allowed for. If between 300-800L is required, hot water production support through the winter months will be necessary.
Light and Lighting
The subject of sleep boils down to the balance and cycle of serotonin (productivity and happiness) and melatonin (to aid sleep) hormone production. High intensity blue light is the champion of serotonin production whereas melatonin develops where the red-light spectrum is more prominent. This typically would follow the outdoor sunrise/sunset cycle and colour rendering.
Therefore, it is important to experience the changing light of the day. This is not to say you need massive expanses of glass, on the contrary. Modern solar control glazing, due to the overheating risk posed, the will have great energy efficiency credentials regarding G-Value and U-Value but could also be cutting out up to 50-60% colour rendering of the red light spectrum. So even sat by a big window (in an office for example), doesn’t guarantee natural light levels.
Many homes and buildings are flooded with high efficiency LEDs which exhibit a predominantly Green/Blue tone. This is fine for active spaces, but in the bedroom and living room spaces use Halogen or Incandescent sparingly but effectively to access the red spectrums of light during the evening hours.
Limiting low frequency Electromagnetic Fields (EMF) generated by mains power is the name of the game in Building Biology. This includes Low Frequency EMF generated by things such as a house hold ring main in the UK due to pulses from the alternating current.
It’s based on the medical understanding that the human brain has its own internal EMF and that this could be susceptible to internal/external fields and especially disrupt our sleep patterns and orientation:
- Awake and alert 30-100Hz
- Awake and drowsy 8-30Hz
- REM Sleep 30-45Hz
- Sleep Phases 4-7Hz
- Deep Sleep 1-4Hz
This can be avoided by splitting the ring into two radial circuits. This doesn’t add much in terms of cabling but does lead to larger consumer units being installed. This also extends to lighting circuits and controls and avoiding two-way switching upstairs and no looped wiring circuits in the bedroom.
Create safe zones around beds of more than 750mm from all fixed sockets and cabling as distance is an effective barrier. Any lamps or pendant cables within this zone should be specified as twisted pairs. In bedrooms use shielded cabling (cost is £60/100m rather than £40/100m) and avoid metal bed frames in bedrooms. Turn off WIFI router via a timeclock switch during sleep hours of 11pm-7am.
Consider the design of locations for domestic hot water cylinders away from bed spaces because of the associated pumps and immersion elements that might operate through the night, and PV inverter placement in the loft spaces of new homes.
High Frequency pulses (Intensity µW/m2), such as mobile phones and Wi-Fi also have an effect.
- Legal threshold set at 10,000,000
- Mobile Phones operate at 250,000
- Blood Brain Barrier effects at 240,000
- Effect on Hippocampus at 100,000
- Double the risk of Leukaemia at 13,000
- Increase in child cancer rate 200
- Impact on sleep at as little as 4
- SBM Range 0.1-5
- Optimal functionality of mobile phone 0.001
Building Biology seeks to make the best of local renewable opportunities, especially if using this local natural asset can offset the import of passive measures from far afield.
Note: Any PV installed should not be recessed into the roof, these should stand proud to enable adequate ventilation to cool the panels and reach their maximum efficiency and output.
Hopefully this has been a useful and gives some practical insight into how some of the service related building biology principles could be adopted on projects. It’s an area Greengauge feel will be very important to our clients over the coming years. Some of services aspects align with Passivhaus principles and this is shared with the building fabric performance principles. Our second Building biology blog focuses on Building fabric.
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