CLPM provide sustainable construction consultancy for architects and homeowners across the UK.
We have recently worked with a couple to help them determine the best approach for improving the insulation levels, and heating and ventilation systems for their home near Wokingham, in Berkshire. The project is a major one as they are re-configuring and updating their two-storey house, which has a separate 2 storey annex, and are hoping to achieve planning soon for a linking extension to combine the two buildings.
The approach we take in projects of this nature is firstly to meet with the clients and understand their objectives, their priorities and any financial considerations. We then spend time looking at the property to assess how it is built. This means checking the property’s walls, floor, roof and windows and its state of repair, before making our detailed recommendations.
In this instance our clients had stated that they wanted to boost the energy performance of their newly refurbished home beyond that required by standard building regs, but only if there was a reasonable payback in terms of running costs. They also stated that they did they want to compromise on the external aesthetics of their home.
When we visited the property, we found that that the majority of the walls were brick built with a cavity in the region of 50mm, except for an area which appeared to be solid brick wall construction. We suggested that the new extension be built using masonry blockwork as this can achieve relatively high effiency levels. As the new extension areas were relatively modest, we felt that using other construction methods would add unnecessary complexity to the build.
We then ran thermal models to estimate the annual energy usage and peak heating load for the different configurations of insulation and window specifications to be considered.
Our suggestion was to clad the exterior of the existing property in 100mm of insulation, with new smooth render applied, and bricks slips to match the original below the window line. The client was keen to install high performance triple glazing throughout, so we advised that glass with reflective coatings and solar-controlled shading would be required to the large areas at the south facing rear of the property to reduce the solar gain.
Internally we suggested our clients apply 20-30mm of insulation to the inside of the external walls. We also proposed they remove the plaster from the skeilings internally, to allow insulation to be added between the rafters. The original ground floors were found to be suspended and ventilated to the exterior, so we recommended that these floors were removed, and a solid, insulated slab be installed in their place. This would then allow underfloor heating to be used easily throughout.
As the property had no mains gas supply, we suggested using either air source or ground source to provide the heating for the building. Underfloor heating is a perfect match for air and ground source heat pumps, as the underfloor runs at around 35C, and matches the heating output of the heat pumps.
Our clients decided to look at using a ground source heating for the project, utilising ground loops within the grounds of the site. We suggested aiming for a 20Kw heat pump which is the maximum size to be able to run on single-phase power supply. For a 20Kw heat pump, 2000 square metres of ground is required, which as the house sits on a large flat plot did not cause a problem.
We suggested that the annexe and the main house could be run with two separate units on the heating control, and hot water supply. We proposed one small hot water tank for the annexe, and a larger unit for the main house, situated in the either the utility or laundry room. There would be a hot water pipe loop to the master ensuite to reduce the delay in receiving hot water at the taps.
Our clients were keen to install mechanical ventilation with heat recovery, using one unit for the house, and one for the annexe. Space would be required for the units, and we suggested some sound deadening to be utilised. We also suggested using a manifold system for the ducting, allowing smaller air ducts to be run through the house. Special attention would be required during construction regarding air tightness to the building to allow the MVHR to operate efficiently. We also highlighted that the kitchen extraction would require to be a closed circuit unit.
We proposed that the heating would be provided by underfloor heating on the ground floor within the screed, with underfloor heating on the first floor with overlay panels.The towel rails in the bathrooms would be heated electrically. The property would also have wood-burning stoves, which would need to be adapted to have dedicated air supplies.
We also suggested that a new external door with a low threshold would need to be fitted to the doorway from the house to allow thermal, and airtightness isolation.
The mains water supply was hard, so we suggested our clients install a water softener, with a fresh water supply to the kitchen sink. We took measurements, and the property had a static pressure of 3 Bar, with a flow rate of around 22 litres per minute. This was not enough for the maximum occupation potential of the building, so we suggested that a pressurisation unit was required to give boost the water supply for the building. A water storage tank was also required which could be placed above the bathroom and landing area in the annexe. We highlighted that structural improvements would be required to support the extra weight of the tank.
A project of this nature means that there is quite a bit of plant that needs to have space allocated for it. We looked at the practical side of our recommendations, and liaised with the client’s architect to ensure that details such as an allocation of space for equipment and plant, replacement floors, deeper sills or soffits would all be included accurately in the designs. For example we suggested positioning the main MVHR unit in the main house roof space close to the linen cupboard, and a small MVHR unit in the roof space for the annexe. We also suggested that the ground floor heating manifold would be situated in the utility room cupboard with first floor heating manifold in the linen cupboard on the landing
Finally, rainwater harvesting was required to supply water to the external taps and future water troughs, with a pump integrated within the tank. We suggested using an accumulator to reduce the frequency of the pump running.
Are you looking for sustainable construction consultancy for your building project? If so CLPM can help!
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