Browse Forums Heating, Cooling & Insulation 1 May 30, 2011 8:23 am How do I interpret the 1st rate energy reports? I've got a 1st rate energy report, and it has zone heat loads in MJ. Most of the heating/cooling specifications are in watts? how do I convert between the two or are they interchangeable? Does the 1st rate report automatically consider room type? (e.g. bathroom should be warmer than bedroom so heating load is a bit higher). Are these energy reports any help for calculating heating/cooling loads or are you better off doing your own manual calculations? my house blog: http://sugarloafdrivebuild.blogspot.com/ Re: 1st rate energy reports 2May 30, 2011 1:34 pm I don't think the 2 are inter workable as the first rate calculation is for energy consumption based on the size, number of power points, appliances specified at build and other factors like orientation vs Sun. As a rough guide I was told for Refrigerated cooling allow 1kW per sq (9.29m2) Can't help with heating or evep though sorry. Re: 1st rate energy reports 3May 30, 2011 7:47 pm maybe these energy reports are helpful. But so far all I can see is we pay money to some guy who runs a government report that compares stuff against a a bull**** list that the government asks to have checked. There's so many assumptions and limitations on these reports, I think they'd be better off as toilet paper. For example... where does passive solar shading fit into an energy report or show up in the rating? I have eaves everywhere, especially over north and west windows, but it doesn't impact the energy rating. The heat/cooling values aren't useful for my heating/cooling contractors so they can't use it, and have to calculate everything over from scratch. Another one - the report assumes heating & cooling loads are per room, but I'm using the radiant/hydronic heating in some rooms (for example laundry and walk in robes), that I would bother to hook up my AC / split to. Seems to me cooling a 500m2 house you would be smart about it and not automatically cool every single room. maybe these energy reports are better than I give them credit for, but from my observations so far - they are not very helpful. my house blog: http://sugarloafdrivebuild.blogspot.com/ Re: 1st rate energy reports 4Jun 12, 2011 7:07 pm These energy reports tend to make certain assumptions about what thermostat levels that the occupants set and how much of the day they would be actively heating. The reports give MJ/m2/year of heating. 3.6 kWhr = 1MJ A 1kW heater would use 1kWh if it was run for an hour. So let us assume a = house area (m2) h = heating (MJ/m2/year) and heating 8 hours a day for 180 days a year Then: Total annual heating (MJ) = a x h Multiply this by 3.6 to give kWhr/year Divide by 180 days (half the year) to get daily heating requirements Divide by 8 hours gives kWhr/hour This will then give you the heating output required by your heater in kW as well. Re: 1st rate energy reports 5Jun 14, 2011 8:01 pm That's helpful to know. From your description it sounds like zoning is not even factored in. For example if you have a 3 floor house or 2 floor house with separate heating thermostats for each floor, and you only heat one floor at any one time, then your MJ calculation would be significantly out. Makes me think these are pretty worthless in multilevel/ multi-thermostat homes. It's worse on cooling - if you are installing ducted splits, then you might only cool individual rooms at different hours vs the whole house. my house blog: http://sugarloafdrivebuild.blogspot.com/ Re: 1st rate energy reports 6Jun 14, 2011 11:58 pm The absolute values are probably not all that helpful. It is more a way of comparing the relative efficiency of the house construction. Occupancy behaviours can cause 50% of the variance in conditioning requirements e.g. letting the sun in by opening curtains instead of turning on the heater, turning off the AC when the cool change occurs and opening all the doors and windows. It is true that a builder can ignore your independent inspection report as it is not part of the contractual arrangement but that is stupid because he cannot avoid fixing… 9 46870 4 6833 Hi there, We’ve recently had plans approved to add a 1st storey addition to our existing house for a growing family in Sydney. With the current cost of building… 0 4298 |