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Nature of project: ecological upgrade of abandoned Garden Centre to low energy family home, straw bale wrap

Client: Josef a Lenka Wihanovi, Náchod, Bražec

Date: 2009

May 2009
Lenka, strawbale wrap, May 2009 (photo by Jindra Sláma)


view from south, abandoned Garden Centre, November 2008
view from south, abandoned Garden Centre, November 2008


view from south, family home under construction, September 2009
view from south, family home under construction, September 2009


September 2009
tripple glazing in clay plastered strawbales, September 2009




September 2009
strawbale south elevation, showing positions of anchors and wallplates


September 2009
strawbale east elevation, wallplates are fixed at heights corresponding to compressed bale size


September 2009
strawbale north elevation


September 2009
strawbale west elevation






kurz amazonails - brožůrka   download presentation   Detail soklu   wrap compression on Youtube
       There isn't much sense in concentrating solely on designing new buildings to the highest energy efficient standards if we don't address sustainability of the old buildings in the first place. This project attempts not only to bring down the energy in use of a refurbished house as close to zero as possible, it does it with a strong focus on use of low energy natural materials.

       Recent grant scheme introduced in May 2009 in the Czech Republic allows the owners of old buildings subsidy, if they decide to make them more energy efficient by wraping them in insulation. However, the scheme completely ignores use of natural materials while supporting highly polluting insulations like polystyrene and mineral wool. Showing off a good will to acknowledge 'hot' environmental issues on governmental level and simultaneously not taking a responsibility for successful execution is typical in the Czech Republic. As a result, the government is encouraging drastic increase in production of polystyrene, with related CO2 emissions that will make the planet unlivable for our children and the future generations. Unfortunately, there are more problems with polystyrene wrap. It damages old structure. Polystyrene suffocates it. It disables breathability and drying. Sealed behind layer of polystyrene, the old structure made of natural materials is exposed to constant presence of moisture, which will surely cause a damage. Nobody will be able to say how long the polystyrene lasts before the old buildings wrapped in it all fall down. Another downfall of using polystyrene is it's questionable durability.

       Ecological upgrade of existing building in Bražec proves that the old buildings upgraded by natural materials with very low ecological footprint benefit on all levels. Here, 50 years old and 400mm wide brick masonry on clay mortar is superbly preserved behind cozy strawbale fur. The whole wall assembly including clay plaster sourced directly from the building site on 270mm thick local strawbales further exceeds any other insulating external wrap option in terms of environment as well as in terms of preservation of exisitng structure. Those walls are able to shield bed weather while staying open to water vapour diffusion (allowing the old masonry to breath). With all it's benefits, this project is tapping into the future.

       Former garden centre built accordingly to drawings produced by architect Rudolf Tencar from Prague in 1948 has magical surroundings. The exotic greenery has matured over the years of neglect. Josef and Lenka bought the abandoned property that includes 3 hectares of gardens and forests as well as buildable land in 2008. Ecological upgrade addressed several issues. Majority of roof structure had been changed and roof was extended over the gables and eaves to provide generous overhangs. Walls opened towards south through large tripple glazed windows. The existing solid - concrete - floors were dug out and replaced with well (LECA) insulated solid limecrete floors. Ceilng was insulated with 540mm thick alyer of tightly stacked strawbales with a clay slab on top. Heating - if at all necessary - will be provided by small wodburning stove.

       The walls were wrapped with strawbales during 12 days of workshop led by foremost British natural building experts amazonails. Thin clay plaster went on uneven existing external brick walls first to smooth out the adhering surface. Well insulated plinth elevates bale wrap at least 350mm above ground. Draining plinth has been built as a cavity wall that goes 600mm below ground and is insulated with LECA. Strawbales were then laid on prefabricated timber baseplate, which was loosely placed on plinth. Wallplates were positioned accordingly to strawbale elevations (see drawings above) and fixed to existing wall with long bolts (running all the way through) prior to strawbale works. The bales were compressed in sections using hydraulic jacks. They were also anchored to the wall by tight "H" shaped triangular anchors at 1200 centres. Each annchor was made with 1 screw eye fixed in brick masonry with polyester strapping as a tie going through the wrap in between blae courses, around piece of timber inserted in the wrap. The strapping is also going around two ash pins (see pictures. Ash was coppiced on site. Greatest attention was paid to openings, which are projecting out of exisitng wall to position windows and doors towards exterior of the wrap.
In cooperation with: amazonails
Nora Kasanická, UK, clay plaster and amazonails workshop trainer

Ing. Zdeněk Nývlt, Náchod, authorized engineer
Ingstav, Náchod, project for building regulations
Radek Ducháč, Topenářství Ducháč, Náchod, plumbing
Jaromír Turínský, Velké Poříčí, window joinery
Miloš Voleský, Náchod, electro installation
Kylar, Náchod, carpentry and roofing


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