The couple were thrilled to ﬁnd their site, but the location came with a signiﬁcant challenge, an incline of 1:13 front to back and east to west. Valley locations can also experience more severe weather conditions than surrounding locations; cold air sinking into the declivity contributes to deep frosts in winter, whilst the south- facing aspect results in high solar gain, increasing temperatures in summer.
The Blee’s had previous experience of building their own properties having already used timber frame on one project and concrete block on three others, but all of these properties had been on level sites. The couple needed a construction method for a house that would be partially underground.
Initially they started to investigate the idea of using separate contractors for the build, one set of builders for the lower ground ﬂoor and specialists to construct the cellar. During a visit to a building show at the NEC, they came across ICF Supplies Ltd and discovered the versatility of the Nudura ICF walling system.
Gisela conﬁrms “We'd seen it featured on TV but didn't realise it could work above and below ground. We got chatting to an expert on the ICF Supplies Ltd Nudura stand and that was the start of a productive relationship!”
Nudura’s ICF system was selected as the optimal build material for the difﬁcult location, being able to fulﬁl the multiple functions required for the build; thermal performance, strength and versatility.
Due to the monolithic concrete core with 67mm of insulation either side, Nudura ICF can attain a very high level of airtightness, complemented by the use of mechanical ventilation and heat recovery. The precision holes needed for the ducting of the ventilation system and other external penetrations through the ICF skin were accomplished by ﬁtting appropriately sized sleeves before the concrete was poured. With a closely controlled 'duct' design, the Stroud Valley Eco House maintains an even temperature throughout the year and achieved an air tightness of 2.37m³(h.m²,).
Nudura ICF is a strong and versatile walling system suitable for buildings of all kinds and in this instance it was the superior choice for the engineered retaining wall forming part of the lower ground ﬂoor subterranean rooms built into the side of the valley. The immense strength provided by the system was easily capable of supporting a large, open plan layout on the upper ground ﬂoor.
The majority of the house was built with 150mm core Nudura block, whilst a curved retaining wall was speciﬁed at 250mm core to better support the areas of highest load. Adapting the wall section from 150mm to 250mm allowed the same construction method to be utilised throughout. The use of NUDURA for the combined retaining/back wall resulted in an additional 55m² of space for use by Andrew and Gisela as a large subterranean garage.
Electrical and computer wiring was easily accommodated by hot wiring channels into the polystyrene to accommodate conduits. The polypropylene webs joining the two polystyrene panels together allowed for quick and easy plasterboard ﬁxing.
The build was completed within 15 months and the lower ground ﬂoor is externally clad in natural Cotswold stone with cream render and red cedar detailing above. Cotswold diminishing stone tiles cover the roof.
Creating an energy efﬁcient home was an important factor for the Blee's. “Our home initially achieved an EPC score of 89 which is a high B rating. The only improvement recommendation was the installation of solar panels, which we already had in place, but we deliberately decided not to connect for the test. With the panels now working our home has now achieved a score of 92 (A rating).”
The EPC estimated that energy usage over a 3-year period would cost £2337. The actual spend on Blee's heating and cooling requirement over the year works out to be considerably lower at less than £1 per day!
“Having project managed a few builds, we've learned that communication with all parties is the key to progress. We've been able to ﬁnd contractors who understood our vision and whose experience is such that they too can offer suggestions to create a shared result. As experienced house builders, we know what we like but have realised that it's important to listen to the views of other professionals – there's always room for learning.
“What initially was just a choice of building method ended up having had a positive inﬂuence on the whole build. After undertaking several building projects, the experience of using Nudura ICF and the relationship with ICF Supplies Ltd has left us in no doubt that if we were to build again we would only consider using Nudura ICF.”