Shropshire's favourite emergency drainage service. This business has been claimed by the owner or a representative. Viessmann products are available from viessmann authorized stocking wholesalers across the us if you need help finding a local wholesaler, please contact a viessmann sales representative via our. Thus, 2000 x 50 = 100,000 btu/hour needed to heat the house & the size boiler needed. The standard thickness is 25mm (eps70) suitable for 16mm hydronic heating pipes and has an r value.