iK News|Zero-carbon housing
A couple of weeks ago, Arup was awarded with the Sustainable Engineer of the Year (the sustainable architect of the year was Architype). The first award was one of the most fiercely contested categories of this year: Arup won because it was the first to design a net zero carbon house that also meets the Code for Sustainable Homes Level 6, the first eco-city masterplan (China), the first net zero carbon housing development concept design (One Gallions Park in East London), the first net zero carbon mixed use development concept design (east Greenwich).
The Lighthouse, by Arup and Sheppard Robson (Sheppard Robson got a commendation as sustainable architect) is acclaimed as the most advanced house design ever produced. It was designed to achieve unrivalled levels of efficiency in terms of the construction method, energy use, CO2 emissions and carbon footprint. It is a little a bit different from the standard housing model: the living areas are located at the top, where they can receive the natural light coming in through the windows and skylights, and all the sleeping areas are at ground level. The residence has been highly insulated with high performance structural insulated panels (SIPS).
This house has a heat loss parameter (HLP) of 0,8.
Katherine Holden, Arup Associate and an expert of sustainable design, explains this characteristic. The Kingspan Lighthouse walls, roof and floor have U-values of 0.11 W/m² K with 284mm wide Kingspan Tek panels, glazing U-values of 0.7 W/m² K, which is with triple glazing, very low emissivity coatings and argon filled cavities, and even an insulated door with a U-value of 0.35 W/m² K.
The 40 degree pitched roof houses 46m2 of photovoltaics (PV) producing up to 4.7kW of electricity; 4m2 of high-efficiency thermal solar panels providing hot water.
Katherine says: "Solar thermal panels can be very effective, even in the UK. For the Kingspan Lighthouse, the supplier, Thermomax, estimated that 4 m² of panels with a collector efficiency of 67% will produce about 2,940 kWh of hot water, which is about 2/3rd of the estimated annual domestic hot water demand. This is equivalent to saving 560 kg CO2/yr compared with gas heating." (via Building)
Let's try to understand these figures with an example.
5 people consume 370 kg of hot water every day. So, we need 12,9 kWh/day or 4.708,5 kWh/yr (it is obtained by using Bernoulli formula c*ΔT*M). With a factor of 0.7, we know that the energetic requirement from the solar source is 3.296 kWh/yr. The solar radiation available could be 1100 kWh/m2 and with a collector efficiency of 67% and 4m² of panels, we can argue that the production is 2948 kWh (more or less the same of what Katherine says).
How much CO2 can we save?
We produce 0,53Kg of CO2 for every kWh: so every year, Lighthouse just produces 0,53x980 = 519 kg of CO2 per year. A conventional house produces 1558 kg of CO2 per year or it needs to burn 735 kg of fossil fuel (2940x0,25).
From an economical point of view, we can cover all the costs in a couple of years. Infact, if the cost of the panels is 750÷1.100 €/m2, the investment would be 3000÷4400€. But with the financial aid from the government (55% in Italy), the final cost would be 1350÷1980€.
- without solar panel: 4708 [kWh/yr] * 0,06 [€/kWh] = 282 €/yr
- with solar panel: (4708 - 3296) [kWh/yr]*0,06 [€/kWh] = 85 €/yr
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