Wonderful news, Sola Roof structures may be tax exempt. The increase in value of a property caused by the addition of a solar energy collector is often property tax exempt. Think about it - in a Sola Roof structure, the entire building is a solar collector, therefore the entire building is tax exempt. If the tax assesor is in a bad mood he may not want to exempt the "normal" parts of the building but the structure, the fabric, control systems, soap solution tanks, heat collection tanks, piping, soap bubble generators, and pumping should be tax exempt.
Each state is different, but this site says most have a provision to this effect and they include URLs for several states provisions: http://www.serconline.org/RenewableEnergyIncentives/propertyTaxCredits.html
This means that if someone builds a Sola Roof residence, business, or greenhouse; it is property tax exempt even if the structure is for personal or business use. California is very generous with solar electric for businesses - SolaRoofers building greenhouses there may have a pleasant surprise. The site above is oriented to the USA, but the UK probably has similar provisions - Harvey Rayner may want to look into this when the tax man comes around to tax his greenhouse - almost everything but the planting beds are part of the solar system. - Bobby