Building Structures

Building Concept - heat loss / gain

In order to meet Building Regulations requirements, any new, or refurbished, building has to meet certain standards to ensure that its heat-use patterns meet national standards and, in fact, ideally improve upon them as the standards are actually the minimum criteria requirements that have to be met.

There are many different ways to achieve these ends and it is inappropriate here to allude to all of these various methods and techniques, suffice to mention the need.

When undertaking the design / re-design of any building, due regard should be taken of all of the site's physical attributes and the building should take advantage of the site, wherever possible, to maximise what Nature has given it, in terms of orientation, elevation, slopes, gradients and ground geology.

What is important is that all strands of the building design - architect, interior design, landscape designer, structural engineer, building services and lighting engineers all understand the design concept, its “whys” and “wherefores”, and utilise all currently available techniques to ensure minimum energy use, both within it's construction and in it's use, combined with the maximum effectiveness, and use, of as much of what “Mother Nature” provides as it is possible and practicable for the particular project to accommodate.

In addition to ensuring that any building is protected against undue heat losses (and gains) - INSULATION, the structure should be as air-tight as is possible to ensure minimum losses through cold air infiltration and warm air escape. In addition it shall exclude all “Cold Bridging” within the construction.

However, the use of artificial heating and ventilation should always be supplemental to the correct use of natural methods wherever this is possible to achieve and should not lead it.

Equipment and furniture (as well as ensuring protection against any potential hazardous situations) should be arranged in such a way as to utilise natural ventilation to its maximum advantage, whilst protecting the subject against drafts and other cold air ingresses.

The use of ground air tubes and stack ventilation are both methods of bringing fresh air into the space with a degree of pre-heating and both help to reduce the reliance upon mechanical forced-air extract ventilation.

Whilst increasing the air-tightness of buildings, could bring with it other problems such as stale, vitiated air, mould growth and increased humidity, it does bring with it, the opportunity to carefully control the condition of the air within certain limits within the building so that undue energy is not wasted in protecting against uncontrolled heat losses / gains from and into it , without resorting to full-blown air-conditioning.

Passive Solar Architectural Design

All built structures will have elevations facing both energy-positive and energy-negative directions.

Dependent upon where the structure is located in the world, the effective solar strike angle will vary in terms of it's the mean solar aspect for any particular structure being considered.

In the UK, the negative face would generally be the north elevation and the sun's mean angle (solar aspect) would be approximately 35° above the southern horizon. This angle, however, varies daily throughout the year and minute-by-minute throughout each day, no matter where the structure is located on the world's surface.

Building elevations in the UK that will exhibit the greatest requirement for energy input, and are the least effective in attracting absorbable free energy, are those north-facing vertical aspects.

The architectural profession is being more and more heavily sanctioned and correctly so, to apply, where this is practicable, techniques that will make the maximum possible use of natural daylight and natural ventilation, whilst at the same time minimising the overheating and glare effects that solar radiation can inflict.

All of this, at the same time as building in, low-emissivity and / or high absorption materials that can ensure that a structure is as energy efficient and reactive as it is practical to be.

These techniques should, wherever possible, always be non-powered and use passive natural effects for their effectiveness and result.

For example, it should be possible, by careful design and consideration, for most, if not all, ventilation, to be capable of being achieved using natural methods and without the use of mechanical aids except for fast and high volume reactivity, ie:- toilet, kitchen and other noxious, vitiated-air extract systems.

It should also be possible, again by the careful use of materials and lateral thinking, to ensure that natural daylight permeates most areas of a structure in usable amounts throughout daylight hours to minimise the need for artificial lighting.

Such methods might include roof lights, light-wells and light-tubes. Natural concentrated light sourced fibre optics bundles could also be utilised to a limited extent in certain circumstances.

With regards to daylight, “North Light” is much more even in terms of light levels and variations though-out daylight hours, as well as light quality, as witnessed by so many artists studios and close / fine tolerance production assembly areas utilising large areas of north-lit space in the past.

There is a school of thought that all such natural light inducing methods should be north face derived. However, so long as measures are in place to protect against solar heat gain, either by shading, or utilisation of some other method, then any naturally derived and usable light has to be welcomed.

Natural daylight, especially that from the east and south-east in the early day, is thought to also benefit well-being, learning and preventing the onset of dementia.

As with utilising solar collecting techniques to heat water and generate electricity, buildings will, and do, warm up due to the effects of the Infra-red part of the spectrum of the very large amount of solar radiation naturally falling upon them.

This heat can be both a boon, and a nuisance. Measures should be in place to both successfully capture and use any heat derived from such availability, but also to protect the structure and its occupants from the detrimental affects of potential overheating caused by such radiation.

Techniques used can range from shading (fixed and automatic) using adjustable blinds and brise soleil , water-flow heat capture, air-flow heat capture to indicate some that are presently available or are currently in development.

“Venturi” and “Stack-effect” Ventilation

Building Regulations call for all occupied structures being constructed at this time, and in the future, to be “Air-Tight” and to be provably so, to achieve it's habitation certificate. However, it also calls for air conditions within the space to be maintained within certain minimum quality levels to maintain health and well-being.

Whilst the first part of the regulations is admirable, and necessary, to minimise the energy consumption required to compensate for the air infiltration that would, and does, occur without such requirements being in place, this very “air-tightness” produces other problems in its wake - primarily air-borne condensation and stale unmoving air created by the natural actions of living.

Both require at least some further energy to be expended in the ensuing forced ventilation requirements needed to overcome, or alleviate these problems.

However, by using careful and possibly lateral architectural design thinking, it should be possible to achieve at least some of the required ventilation needed using natural stack-effect and / or by employing the venturi effect of the wind passing over various strategically located external outlets.

To ensure that a venturi effect is always operable, such outlets could be fitted with, say, wind-movable cowls similar to those that used to be seen on fire-place chimneys to ensure that there was sufficient draw and to stop smoke blowing back into the room.

In addition, if the system is well enough designed, the air being drawn out will pass through a heat-recovery system that should be capable of recovering and transferring 70-80% of the heat that is embedded within that stale extracted air into the fresh air that will be required to replace it.

With careful consideration and design, both of the structure and of the system, these effects should be capable of being achieved, in many cases, in a fully passive manner.

Light Tubes & Light Wells

If viewed as an electrical use pie-chart, then the largest single portion of this pie nationally in both domestic and commercial applications, is eaten up by artificial lighting.

Apart from ensuring that where possible during daylight hours, and practicable (ie:- where physical and process safety are not issues) - lighting should be always turned OFF. Where this is not possible, then low energy lighting sources should always be used.

However, the design of all properties be they domestic, commercial or industrial, could utilise daylight much more than it does already and utilise it much better where it already does so. There should be much more consideration applied to the accomplishment of such daylight utilisation.

The use of light wells is one technique that can bring natural daylight into internal enclosed areas, and additionally, dependent upon their design, these wells can have a secondary effect by being able to be used to provide for some of the stack-effect ventilation previously mentioned.

Another technique could be to use a light-tube, where a clear light capturing unit is mounted on the external roof and this captured light is transmitted into the required space via an internally, highly polished, flexible tube.

Within the space to be illuminated, the tube is connected to an opaque diffuser mounted at the ceiling level of the space and which distributes the light to the space around it.

Very high local light levels can be achieved using such techniques and they, in turn, reduce the reliance upon energy-using artificial lighting within the space during daylight hours.

By using a concentrator mechanism, the light captured at the external element mentioned above, a fibre optic bundle, instead of a tube, can be “powered” by this natural light and can be used to provide all manner of low level lighting within a space or spaces in any structure.

Light Control

Artificial light is over-used in all developed countries of the world (and now in some less-developed ones as well) because the human being appears to be averse to simply turning it off when it is not needed.

Apart from ensuring that where possible during daylight hours, and practicable (where physical and process safety are not issues) - lighting should be always turned OFF. Where this is not possible, then low energy lighting sources should always be used

To achieve the best from artificial lighting, it is essential that it is designed correctly for the particular purpose within the designated area in the first place.

However, utilisation of the current lighting code levels should be for guidance only and the application of common sense and experience to ensure the maximisation of source utilisation and the minimisation of energy use are deemed paramount.

A new lighting code has recently been published where the old levels and measuring points have been totally rethought. Hopefully this will have the effect of reducing designed lighting load.

This use of artificial lighting should always be supplemented by the correct use of daylighting wherever possible. Equipment and furniture (as well as ensuring protection against any potential hazardous situations) should be arranged in such a way as to utilise daylight to its maximum advantage, whilst protecting the subject from potential solar glare. (use “North Light”?)

The use of light wells and light tubes are both methods of bringing natural usable light into the space and help to reduce the reliance upon artificial light during daylight hours.

The largest waste of energy is the leaving of artificial lighting ON when the space is unoccupied.

Added to the daylight use techniques, controls are available that can automatically monitor the light levels within a space and are capable of reducing the proportion of artificial light in relation to natural light using dimming techniques until the luminaires are completely shut off. (they can also reverse the situation as external daylighting levels fall)

In addition, the use of presence / absence detectors within any space can ensure that if no-one is in the space, ALL artificial lighting (with the exception of safety lighting) will remain off and not using any energy when it is not required to do so.

Step 1) Ascertain use for the space and therefore it's code guidance requirement, (also taking into account architectural / client thoughts as well as any plant / furniture required for any such area)
Step 2) Design the artificial lighting required to satisfy code guidance requirement using low energy sources, common sense and experience, (also taking into account architectural / client thoughts as well as any plant / furniture required for any such area)
Step 3) Apply daylighting design to the artificial lighting design and review as / if required, (again taking into account architectural / plant needs)
Step 4) Apply automatic controls to both daylight and artificial results, (again taking into account client operational requirements)
Step 5) Review whole entity and adjust / amend to suit if required.

With acknowledgement for use of images to: