FEEDBACK Is natural gas the right choice for new builds? I agree, we should not be designing in natural gas systems of any kind now combined heat and power (CHP) included. By the same token, we need to be cognisant of the global warming effects of refrigerant leakage of heat pump systems. The sooner we get safe low global warming potential (GWP) refrigerants into commercial use the better. Meanwhile, engineers should be getting familiar with the safe design, use and maintenance of natural refrigerants. Edward Murphy Ammonia is, to me, the best choice. Ammonia has been around for years; if it leaks, it decays into nitrogen very quickly. With regard to safety, in small quantities, humans react by getting away from the pungent smell. In large quantities, yes, its toxic but so is natural gas, and were relaxed about having that piped into our homes. Gareth Young Ahead of Build2Perform, CIBSE LinkedIn Group discusses alternatives to natural gas Are you still designing natural gas heating systems in new builds? The decarbonisation of heat is a critical and urgent challenge for the UK. Existing building stock requires complicated retrot, but new builds are a comparatively simple problem. Surely there is a tremendous opportunity to get it right rst time. Anything built without low carbon heat today is creating retrot problems for the future. With declarations of climate emergencies, why are we still designing natural gas heating systems in new builds? An obvious answer might be cost, but is that the only answer? What is the case for gas in new builds, and how can built environment professionals accelerate the uptake of low carbon heating? Andy Ford Good job there are some great heat pumps out there! Heating, cooling and domestic hot water from ambient loops throughout mixed-use single building and developments offer workable energy sharing/ heat recovery. William Littlewood Join the conversation We want to hear from you. Talk to us. We, with the Department for Education, have created a template for a modular primary school no gas! Jeff Anderson @CIBSEJournal CIBSE LinkedIn www.cibse.org Subscribe to our newsletter Receive our top stories about building services engineering. Sign up at cibsejournal.com The interseasonal energy-transfer system seems very hopeful; Im trying to specify it on an ofce block Im designing, but there are commercial issues the extra cost of building the thermal store. However, with annual coefcient of performance (COP) in the order of 8:1, its all good news. Gareth Young Indeed. Great refrigerant. As you are probably aware, some downsides make it expensive short term, but that is because it s never had the research and development investment it deserves. Edward Murphy Heat pumps seem, to me, to be the way forward. I m currently designing the heating and cooling system for an ofce block in London without any gas supply. Gareth Young Great question does this include remote gas combustion via heat networks? This is often a planning policy obligation and networks seldom have decarbonisation strategies, as expensive technology such as CHP has been locked into the nancial model and requires pay back before any new low carbon technology can be considered. Greg Jones To the rst question, I would say yes. In many ways, heat networks and existing district heating are the obvious targets to improve the existing stock, but we want to understand what drives new build, and your comment on nancial models feels signicant. Andy Ford Making the case for direct gas-fired water heaters High storage risks The efciency and performance problems associated with storing high volumes of hot water agged up in the article Hotel study reveals predicted hot water use is double the reality (CIBSE Journal, April 2019) could be solved by making better use of direct gas-red water heaters (DGFWHs). The problems highlighted in the article appear to be related to indirect hot-water systems with high storage capacity, and it refers to the difculty some engineers have in sizing the storage requirement accurately. It 20 November 2019 www.cibsejournal.com CIBSE Nov19 pp20-21 Letters.indd 20 25/10/2019 14:40