Green Building Bible, Fourth Edition |
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These two books are the perfect starting place to help you get to grips with one of the most vitally important aspects of our society - our homes and living environment. PLEASE NOTE: A download link for Volume 1 will be sent to you by email and Volume 2 will be sent to you by post as a book. |
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Posted By: ringiI questions if the "mhrv rate" is correctly recorded for most homes....
It is also well know that people breathing add more water to the air when the RH is lower. Like with plants, showers, cooking, uncovered wc etc.
Hence using average values for a building with such a low RH is questionable, but djh may not wish to spend a day with a plastic bag over his head….
The only way to get a good measurement of RH is to use a “wet bulb†and a “dry bulb†thermometer recording the output of both of them. (About £30 without calibration, £200 with NIST traceable calibration) I don’t think any of us have such equipment.
Posted By: djhWell, we're hygroscopic objects the same as wood, so we behave like a block of wood ...
Posted By: WillInAberdeenDJH is extracting 9kg/d of water from his house…That's assuming that the air going into the extract vents is at the measured RH. CO₂ can vary widely across the room so I expect humidity can, too (as is pointed out in the Trouble With Humidity document Steamy linked on the previous page). RH sensor in the extract duct, anybody?
Posted By: ringiPosted By: djhWell, we're hygroscopic objects the same as wood, so we behave like a block of wood ...
No our lungs are a lot more active then that and works hard to keep the RH high enough inside of them. Hence dehydration was a big issue when Everest was first being attempted. Live plants with leafs on them are also more active the a lump of wood.
Posted By: Ed DaviesPosted By: WillInAberdeenDJH is extracting 9kg/d of water from his house…That's assuming that the air going into the extract vents is at the measured RH. CO₂ can vary widely across the room so I expect humidity can, too (as is pointed out in the Trouble With Humidity document Steamy linked on the previous page). RH sensor in the extract duct, anybody?
Posted By: ringiThis is all making me questions if duct heaters are a good option, as it is hard enough to set the HRMV rate without having to think about the effect on heating as well.
Posted By: djhWhat complicates my system is the desire to run the heating at night on E7,
Posted By: Ed DaviesRight, but why wouldn't an ordinary convector heater do the same thing? Could still be run off E7, just using the structure of the building rather than special bricks to store the heat.
Posted By: djhWhat complicates my system is the desire to run the heating at night on E7Can you get a couple of large storage heater, say 35 kWh ones, put them in an insulated box, plumb them into the MVHR system so that they are after the heat exchanger i.e. on the pipework to the rooms.
Posted By: Ed DaviesAm I right to assume that the Passivhaus goal of heating with ventilation air only assumes that heating runs 24 hours?
Right, but why wouldn't an ordinary convector heater do the same thing?
Posted By: Ed DaviesDJH, what temperature does your duct heater heat the air to? 50 °C or less?
Posted By: djh
I think I put the set point at 45°C, from an abundance of caution (or nervousness!)
It's notable that quite a lot of the heat goes into the duct walls and thence into the first floor structure. I can roughly track the duct layout using my IR thermometer in the mornings. The temperature at the supply terminals is noticeably warmer for those with shorter duct lengths. I'm quite content as long as the heat goes into the house somewhere though.
Posted By: ringiSo you are "kilm drying" all the wood in the first floor structure, what else are you kilm drying at assuming at least 30c?
Posted By: djhPosted By: ringiSo you are "kilm drying" all the wood in the first floor structure, what else are you kilm drying at assuming at least 30c?
I assume I kiln-dried it all last winterhttp:///newforum/extensions/Vanillacons/smilies/standard/bigsmile.gif" alt="
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All the usual: insulation, plumbing, electrics etc. I doubt there's much more stress than from central heating, DHW distribution and hot summers in more normal houses.
Posted By: WillInAberdeenInteresting that the vapour creation rate almost balances the extraction rate (mystery solved?). What happens in the summer?Yes - well worth watching what happens through the year.