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Insulation and air tightness standards
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kenneal - lagger
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PostPosted: Fri Jan 26, 2018 4:45 pm    Post subject: Reply with quote

A further note on the above for the uninitiated. This article refers to a house in Australia in the southern hemisphere so if you're in the northern hemisphere all references to the north should be replaced with south. All main rooms and windows should face south and the eaves shading of those windows will also be on that elevation.

The article refers to R values which are used in the US and Australia and refer to the insulation value, the Resistance, of the individual element of insulation. With R values the higher the value the better the insulation.

In this country U values are more often quoted for the complete finished wall and would be in the range of 1 to 1.2 W/sq m/deg C with 1 being the better value in that it lets less watts of heat through.

Both values refer to the heat loss per unit area be it sq m in Europe or sq ft in the US at one unit of temperature. Generally deg C in Europe and deg F in the US.
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cubes



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PostPosted: Fri Jan 26, 2018 8:04 pm    Post subject: Reply with quote

Talking of Passivhaus, in the local rag

First glimpse today of ‘passivhaus’ new homes being built in Bowthorpe
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emordnilap



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PostPosted: Tue Jan 30, 2018 12:39 pm    Post subject: Reply with quote

Note that some HRVs draw air into the house (ie, it's not an extractor fan), relying on air pressure created to push out damp air.

The Kiltox is configured thus, so is useless in damper climates.
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kenneal - lagger
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PostPosted: Tue Jan 30, 2018 3:39 pm    Post subject: Reply with quote

All MVHR systems have two fans, one drawing air out and one drawing air in. The two streams of air pass each other either side of a thin metal plate which transfers heat from one stream to the other. Air inside the house is almost always at a higher humidity than air outside so bringing air in will almost always reduce the humidity in the house. The more humid warm air from the house goes past the cooler/cold less humid air and the moisture from the inside air condenses onto the heat exchange plate giving up that heat to the incoming air as well. The condensation is drained away to waste. Because the incoming air is warmed its humidity is reduced.

So a MVHR system will work no matter how damp the climate.
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Last edited by kenneal - lagger on Tue Jan 30, 2018 4:59 pm; edited 1 time in total
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vtsnowedin



Joined: 07 Jan 2011
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Location: New England ,Chelsea Vermont

PostPosted: Tue Jan 30, 2018 4:05 pm    Post subject: Reply with quote

kenneal - lagger wrote:
All MVHR systems have two fans, one drawing air out and one drawing air in. The two streams of air pass each other either side of a thin metal plate which transfers heat from one stream to the other. Air inside the house is almost always at a higher humidity than air outside so bringing air in will almost always reduce the humidity in the house. The more humid warm air from the house goes past the cooler/cold less humid air and the moisture from the inside air condenses onto the heat exchange plate giving up that heat to the incoming air as well. The condensation is drained away to waste. Because the incoming air is warmed its humidity is reduced.

So a MVHR system will work not matter how damp the climate.

While they may have two fans I can't imagine why one would not work just like the draw of a chimney draws air in from every available opening. I've seen several of these here and do not recall ever seeing a drain line but perhaps our dryer conditions and the use of wood heat as primary heat source render a drain unnecessary or the exhaust air is on the bottom and drops away and out the wall so water freely drains out to the outside.
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kenneal - lagger
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PostPosted: Tue Jan 30, 2018 4:53 pm    Post subject: Reply with quote

The idea is to maximise the efficiency of the heat exchange process so to minimise the loss of warm air from the system two fans are used. The power used would be virtually the same as if only one fan was used as the input fan is acting with the extract fan rather than against a back pressure. These systems wouldn't be of any use in Woodburner's house as he's losing all his heat through excess ventilation anyway.

Having said all that, Doomer that I am, I wouldn't design a house to be reliant on a Mechanical Ventilation system with Heat Recovery (MVHR) any way as I think that in the near future the parts, the filters and replacement fans, won't available and the power, albeit less than 100W, could be a problem as well.

I design air tight houses with trickle vents in the window casements and openable windows and with ducted air supplies to stoves so that it will be possible control the ventilation rate in the building in all weathers, hot/cold and still/windy without using excess fuel. The Ventive system of passive stack heat recovery ventilation looks good and I look forward to using such a system myself in the near future.

If a fossil fuel or electric heating system is installed I always advise that a secondary heating and cooking system is available in case of power/fuel cuts in supply. As most of the houses that I design are in rural areas or small towns this is usually in the form of a flat topped wood burning stove although I am experimenting with various configurations of Rocket fire/stoves for this purpose.

The use of wood in large towns is increasingly being frowned upon and may soon be subject to new smokeless zone legislation. In this case I would advocate fitting a chimney and installing a gas fire which has no electrical input so that heat can be had in case of electricity cuts. In the future when TS has HTF the chimney could be used for wood burning and a stove cobbled together in some way.
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vtsnowedin



Joined: 07 Jan 2011
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Location: New England ,Chelsea Vermont

PostPosted: Tue Jan 30, 2018 5:33 pm    Post subject: Reply with quote

kenneal - lagger wrote:
The idea is to maximise the efficiency of the heat exchange process so to minimise the loss of warm air from the system two fans are used. The power used would be virtually the same as if only one fan was used as the input fan is acting with the extract fan rather than against a back pressure. These systems wouldn't be of any use in Woodburner's house as he's losing all his heat through excess ventilation anyway.

Having said all that, Doomer that I am, I wouldn't design a house to be reliant on a Mechanical Ventilation system with Heat Recovery (MVHR) any way as I think that in the near future the parts, the filters and replacement fans, won't available and the power, albeit less than 100W, could be a problem as well.

I design air tight houses with trickle vents in the window casements and openable windows and with ducted air supplies to stoves so that it will be possible control the ventilation rate in the building in all weathers, hot/cold and still/windy without using excess fuel. The Ventive system of passive stack heat recovery ventilation looks good and I look forward to using such a system myself in the near future.

If a fossil fuel or electric heating system is installed I always advise that a secondary heating and cooking system is available in case of power/fuel cuts in supply. As most of the houses that I design are in rural areas or small towns this is usually in the form of a flat topped wood burning stove although I am experimenting with various configurations of Rocket fire/stoves for this purpose.

The use of wood in large towns is increasingly being frowned upon and may soon be subject to new smokeless zone legislation. In this case I would advocate fitting a chimney and installing a gas fire which has no electrical input so that heat can be had in case of electricity cuts. In the future when TS has HTF the chimney could be used for wood burning and a stove cobbled together in some way.

Wood burners house aside several of the houses being built here are to passive house standards and use wood for primary heating.
The heat exchanger is just to recover heat from stale air that needs to be vented because the house is too tight to provide healthy air without it being deliberately brought in. It is not just a glorified bathroom exhaust fan. The primary heat is the wood furnace or stove in the basement and a 3500SF house can be heated here with less then three cords of good hardwood a year. These houses almost all have hard wired backup generators and have a second heating system often propane fired radiant in the floors. And of course if all else failed the windows still open when desired. The houses are status symbols built by the ten percenters and though very expensive to build are very energy efficient once completed and serve their owners well.
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kenneal - lagger
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PostPosted: Tue Jan 30, 2018 5:59 pm    Post subject: Reply with quote

vtsnowedin wrote:
..... several of the houses being built here are to passive house standards and use wood for primary heating.
The heat exchanger is just to recover heat from stale air that needs to be vented because the house is too tight to provide healthy air without it being deliberately brought in. ...


You're missing the point here, VT. The house isn't built "too tight" it's built tight enough so that heat isn't lost though excess ventilation. Adequate ventilation is then deliberately provided by the MVHR system. The air loss should be no more than 0.6 Air Changes/hr at 50pa pressure. The ventilation system is part of the initial heat saving design not an afterthought.

In a PassivHaus certified system the heating requirement should be capable of being supplied by warming of the input air by a heater in the MVHR system and be not more than 15kWh/(m²yr) total. If the heat loss is such that any further heating is required it wouldn't get PassivHaus certification.
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vtsnowedin



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PostPosted: Tue Jan 30, 2018 7:39 pm    Post subject: Reply with quote

kenneal - lagger wrote:
vtsnowedin wrote:
..... several of the houses being built here are to passive house standards and use wood for primary heating.
The heat exchanger is just to recover heat from stale air that needs to be vented because the house is too tight to provide healthy air without it being deliberately brought in. ...


You're missing the point here, VT. The house isn't built "too tight" it's built tight enough so that heat isn't lost though excess ventilation. Adequate ventilation is then deliberately provided by the MVHR system. The air loss should be no more than 0.6 Air Changes/hr at 50pa pressure. The ventilation system is part of the initial heat saving design not an afterthought.

In a PassivHaus certified system the heating requirement should be capable of being supplied by warming of the input air by a heater in the MVHR system and be not more than 15kWh/(m²yr) total. If the heat loss is such that any further heating is required it wouldn't get PassivHaus certification.

We are talking past each other and often saying the same thing. Time to let it drop.
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kenneal - lagger
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PostPosted: Thu Feb 01, 2018 5:38 pm    Post subject: Reply with quote

We might be talking past each other although I don't think that we are saying the same thing. Your answer above about the building being built "too tight" shows a definite misunderstanding of the logic so I can't let it go just yet.

In your climate you wouldn't go to bed at 20 below with a gale blowing and leave a window open would you? But that is just what you are doing by living in an unsealed house. The cracks and leaks in an unsealed house are equivalent to leaving a window open.

If you need to have a window open you can always open one but if you want to close that window caused by the leaks you can't. You can't close that windows worth of leaks and open a trickle vent which might be what is needed in the bedroom on the night described above.
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vtsnowedin



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Location: New England ,Chelsea Vermont

PostPosted: Fri Feb 02, 2018 12:23 pm    Post subject: Reply with quote

kenneal - lagger wrote:
We might be talking past each other although I don't think that we are saying the same thing. Your answer above about the building being built "too tight" shows a definite misunderstanding of the logic so I can't let it go just yet.

In your climate you wouldn't go to bed at 20 below with a gale blowing and leave a window open would you? But that is just what you are doing by living in an unsealed house. The cracks and leaks in an unsealed house are equivalent to leaving a window open.

If you need to have a window open you can always open one but if you want to close that window caused by the leaks you can't. You can't close that windows worth of leaks and open a trickle vent which might be what is needed in the bedroom on the night described above.

The passive houses I am talking about are fully designed for it and the ventilation system was planned from day one. The expression "too tight" only means that the ventilation system has become a necessary part of the design not an after thought. You are arrogantly implying that we Americans are rubes that don't know how to build a house or a heating system.
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kenneal - lagger
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PostPosted: Fri Feb 02, 2018 2:08 pm    Post subject: Reply with quote

I didn't say anything about a heating system and your run of the mill houses are probably tighter than ours but I doubt that you usually build those houses to a tightness of less than 0.6 AC/hr at 50Pa. I was merely querying whether you would contemplate going to bed with a window open.

Your description of the extent of the heating system on the passive houses/PassivHauses doesn't correlate with the sort of heating that is fitted to a PassivHaus in the UK or even in Germany where the winters are more your sort than ours. Those systems are much larger so I was querying whether those houses were Certified by the PassivHaus Institute or not.

I was not being arrogant in any way whatsoever.
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vtsnowedin



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Location: New England ,Chelsea Vermont

PostPosted: Fri Feb 02, 2018 2:34 pm    Post subject: Reply with quote

kenneal - lagger wrote:
I didn't say anything about a heating system and your run of the mill houses are probably tighter than ours but I doubt that you usually build those houses to a tightness of less than 0.6 AC/hr at 50Pa. I was merely querying whether you would contemplate going to bed with a window open.

Your description of the extent of the heating system on the passive houses/PassivHauses doesn't correlate with the sort of heating that is fitted to a PassivHaus in the UK or even in Germany where the winters are more your sort than ours. Those systems are much larger so I was querying whether those houses were Certified by the PassivHaus Institute or not.

I was not being arrogant in any way whatsoever.

No you were not asking any questions "querying" as you put it. You were "instructing the ignorant". Your arrogance was dripping from every word.
A house does not have to be "certified" by any institute to be of the highest quality as fancy paperwork holds not one BTU in place.
You're being a pompous ass and your not half as smart as you think you are.
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