STYROFOAM and the Underhill House project
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Building Solutions Underhill House project

Introducing Underhill House and Hill Barn This brochure documents Dow Building Solutions’ involvement in the Underhill House and Hill Barn project, an inspirational and innovative development of a strikingly modern, environmentally-sustainable house under the ruins of a 300-year old barn in the UK’s Cotswolds. We set out the story of the development, highlighting how STYROFOAM™ and other products from Dow Building Solutions have been used to help turn an initial concept into a reality for a pioneering British architect and her family - creating the first ever certified quality approved...

Overcoming planning obstacles with an ambitious design Located in the heart of the English Cotswolds, Hill Barn was a derelict 300-year old barn situated in a prominent and beautiful location on a hillside in an Area of Outstanding Natural Beauty (AONB). Designed to safeguard an important local environment, the AONB designation made the prospect of obtaining planning permission for any development of the barn a daunting prospect. Despite a housing moratorium in the district of Stratfordupon-Avon, the local planning authority was impressed with the project’s eco-credentials and its...

A truly sustainable home Not only is the external form of Underhill House designed to minimise environmental impact, the interior form and construction materials were carefully chosen to make the building as environmentally sustainable as realistically possible. The effort paid off for the architect, with Underhill House becoming the first in England become a certified, quality-approved Passive House in January 2010. Underhill House is entirely glazed to the south. The rest of it is earth-sheltered and highly-insulated, creating the perfect passive solar design. In addition, the structure...

The Passive House concept The Passive House concept was developed in Germany (where it is known as Passivhaus) in the mid 1990s and is widely regarded as the world’s leading standard in energy efficient construction. The standard requires very high levels of insulation, a design that makes the most of solar energy and that creates a well-sealed building. The standard does not dictate the design or external appearance of a structure. It’s simply a method of calculating the amount of insulation, glazing, thermal mass and other design properties required to make the best use of a building’s...

Surrounded by STYROFOAM-A: delivering thermal performance and strength Central to Underhill House achieving Passive House certification was the thermal performance and strength of a range of products manufactured with STYROFOAM-A blue extruded polystyrene. Produced at Dow’s facility at King’s Lynn in the UK, STYROFOAM-A products FLOORMATE™, ROOFMATE™ and PERIMATE™ insulate the floor, roof and basement walls of the structure. FLOORMATE 300-A proved to be the real star of the show when it came to insulating Underhill House. Because it resists moisture and has a high compressive strength,...

STYROFOAM-A for tough insulation demands As regulations around the thermal performance of buildings become tighter in the drive towards more energy-efficient buildings, insulation that can perform in demanding environments will play a vital role. STYROFOAM-A products are manufactured in the UK using technology that takes CO2 from industry and uses it as a blowing agent in order to create blue extruded polystyrene foam with a Global Warming Potential (GWP) of less than five. STYROFOAM-A also maintains properties the building industry has come to rely on from STYROFOAM insulation products -...

FLOORMATE 300-A boards were laid beneath the entire floor slab of Underhill House, a growing practice in residential buildings and one which could support more energy efficient housing in future. High compressive strength, excellent water resistance and long term durability make ROOFMATE the first choice of some of the UK’s biggest names in roofing. Because it resists moisture and is very durable with a high compressive strength, FLOORMATE 300-A is ideal for below-slab insulation, which is the right design choice when aiming for an ‘envelope’ of continuous insulation that minimises heat...

PERIMATE DI-A Insulating walls below ground requires a product that is highly-moisture resistant. PERIMATE DI-A boards have vertical channels cut into one face, to drain water away, with a filter fabric bonded to the face to prevent soil particles blocking the channels. The below-ground walls of the earth-sheltered, Underhill House were covered with tanking membrane before being surrounded by FLOORMATE and then PERIMATE DI-A boards and backfilled. The boards not only insulate the structure, but protect tanking material from damage from backfill material. They also drain water away from the...

Why did you choose this part of the UK to create your design, and why select such a challenging site? It’s been a life-long ambition to design and build my own house - and what better place to do that than the area where you grew up? My father owns the land the original barn was built on and we used to come up here for picnics when I was a child. We can even see the church my husband and I got married in from the site, so it’s a very special place for us. Why was getting Passive House certification so important to you? Passive House design achieves a staggering 90% energy saving compared to...

Once the concept was agreed and planning permission achieved, how technically difficult was the build? Well, suspending a 300-year-old barn in mid-air whilst we excavated and built a brand new building beneath it was quite a challenge! This obviously required specialist help from very brave structural engineers. Installing the pre-cast concrete sections and waterproofing also required support from specialist contractors. Installing the various STYROFOAM-A products was very easy to manage and, after initial guidance from Dow Building Solutions, all of this was managed by someone with no...