raise buildings on stilts. This would be most straightforward with a steel frame option that would serve both individual houses and multi- storey apartments. The open ground floor would provide parking space that could be evacuated on the announcement of flood warnings (Figure 5.4).
Alternatively, there are numerous waterproofing systems available, some of which consist of a surface coating. For example, a paint- on material Penetron creates a tight crystalline web within the structure of concrete, making it watertight. However, traditionalists will claim that the only reliable, long-life technique able to withstand the pressure from serious flooding is tanking. Figure 5.5 illustrates how this is achieved in a high thermal mass structure.
At the same time, doors and windows that extend below dado height should have watertight seals.The most fail-safe method would
be inflatable seals triggered manually by the same mechanism as that used in vehicle air bags.
The most effective design for flood-prone areas involves the inclusion of a semi-basement. This can be reasonably cost-effective if the excavation adopts the cut-and-fill method, avoiding earth removal. This method has the advantage of raising the ground floor at least one metre above ground level. The BREEAM Eco- homes recommendation is:
Where assessed development is situated in a flood zone that is defined as having a medium annual probability of flooding, the ground level of all dwellings and access to them and the site are designed so that they are at least 600mm above the design level of the flood zone.
(EcoHomes and the Code for Sustainable Homes, BRE, 2007) In either case, the problem of access for the disabled remains to be resolved.
A detailed cost analysis will be necessary to determine which is the more cost-effective between the steel frame and masonry systems. The advantage of the former is that much of it can be prefabricated, whereas the latter has better thermal mass.
In Holland there is a growing appetite for homes with in-built flotation chambers. However, these are mostly intended as permanent floating homes which can rise and fall as water level dictates. The time may come when the shortage of land following sea level rise will make this an option for the UK. It would seem to be an extravagance at present.
Appliances will need special attention. A retrofit flood protection programme in South Yorkshire has provided ‘bung’ seals for WCs; not elegant but presumably effective, pending design
changes. Sanitary ware manufacturers will have to be persuaded to provide basins, baths and showers with screw-down plugs and without overflow openings.
In the 2007 floods in Gloucestershire the inundation of a major electricity substation was just avoided. Had it been flooded, thousands of homes would have been without electricity perhaps for weeks. In flood risk areas like the Severn and Thames valleys it would be prudent for roof PVs to serve dual AC/DC appliances and fittings as well as keeping a bank of batteries fully charged.
The rising demand for new houses and the pressure to bring many of them within the range of first-time buyers highlights the dilemma facing developers and designers on the one hand and the government responsible for standards on
48 Building for a Changing Climate
300 mm insulation
100 mm insulation
internal walls (thermal mass) Ring beam
Aerogel boards int. lining Triple glazing
pre-cast beams with fairface exposed soffit prefab insulated timber framed panels within steel structure
75 mm rigid insulation pre-cast conc. beams
Void (Car space) 150 x 150 mm steel columns RSJ Ground level RSJ RS channel external insulation with waterproof render
Steel stress plate
100 mm dense concrete block
the other. Is it a case of the best being the enemy of the good? The purpose of this and subsequent chapters is to consider the design challenge assuming the worst case climate change outcome. Given a near miracle, CO2 emissions may be stabilized before runaway climate change is triggered. However, the prospect of peak oil and rapidly diminishing reserves is beyond the scope of miracles. Energy efficiency and fossil free alternatives for power are not options but inevitabilities.
Some home buyers will be aware of the value of investing in a near climate-proof home, ‘but this translates only weakly into buying
preferences: it ranks well behind the key requirements of price, size and location. This is insufficient to motivate housebuilders or, through them, the rest of the market’ (Callcut Review, 2007, p89).
Only radical revision of the building regulations will succeed in delivering the quality of homes that will withstand the impacts of the coming decades.
Figure 5.5 is an outline idea of the kind of construction that should protect against high temperatures and all but the worst of flash floods. It has traditional tanking to at least 1m above ground level and inflatable seals to doors and Figure 5.5 Suggested construction details of near-climate-proof houses
300mm insulation
U-clamp
Concrete ring beam anchored to walls
pre-cast conc. beams with exposed soffit
phase change material plaster
tile floor finish
50mm insulation tanking SCALE 1 : 10 strip foundation reinforced against ground shrinkage engineering brick to dpc
damp proof membrane 140mm high density blocks insulating render
marine-type seals to windows.There would also be measures to protect against upsurge via appliances. High thermal mass is provided by external walls, floors and partitions. PCM plaster could enhance the thermal mass.
Extra structural strength, such as a reinforced concrete ring beam securing the roof members, is provided to protect against hurricane level storms. Reinforced foundations protect against damage through ground shrinkage, which can be an effect of a severe drought – also one of the predicted impacts of climate change. Folding shutters protect quadruple-glazed windows. Masonry construction guarantees that the highest air tightness standard will be achieved in conjunction with heat recovery low power mechanical ventilation. The warm air could be enhanced by a ground source heat pump. The extended south facing 30° roof would be covered with PVs and solar thermal panels. Substantial eaves overhangs will offer solar shading in summer. In winter the south elevation would make the most of passive solar gain. This could be the nearest we ever get to a zero carbon house.
There will be those who argue that such building practices will involve much greater embodied energy than the timber frame alternative. Expended energy is a function of materials and construction on the one hand and life expectancy on the other. On this basis high thermal mass masonry homes could show a much better balance in their energy account than their timber counterparts.Then there is the matter of robustness.
Advocates of timber may point to Tudor timber frame buildings that are still standing after 500 years. However, these were usually constructed of hardwood, mostly oak, often of a cross section with a massive margin of safety (redundancy). Even so, oak is not infallible. In 1983 I was commissioned to carry out a restoration survey in the President’s Lodge in Cloister Court at Queens’ College, Cambridge. This included a timber long gallery placed above a brick cloister. A massive oak ‘keel’ beam running the length of the centre of the cloister was supporting the floor of the long gallery. I discovered this had split along its length at the
point where floor joists were halved into it. Engineers consulted on the matter considered that there could have been a catastrophic collapse at any time, given the right wind loading. In mitigation, the beam was at least 400 years old (Smith, 1983).