Chimney in airtight passive house

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LouisCribben

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Am I correct in thinking that for a house to reach the passive house standard, a chimney is not possible ?

Obviously an open sitting room fire is out of the question, because it makes air tightness impossible, but what about a solid fuel unit ?

I'm thinking that no matter how a chimney is constructed, it always creates a thermal bridge to the outside. Am I correct.
 
Practically speaking, yes, there should be no chimney in a passive house.

Not only is the air tightness a factor, notwithstanding a room sealed stove, but more importantly the thermal bridging of the chimney could mean that passive levels couldnt be met.
 
Louis
Whilst that may be correct to the letter of the standard, it's you who's living in the house, not the Institute..........a room-sealed unit, with a good flue detail, will have little practically-meaurable difference in the performance of the house - from an economics point of view.

You can have passive performance levels, and still not get a PHI cert, so don't go beating yourself up over this.

Look at it this way - if you open a window for fresh air, it'll make a bigger difference...........

...don't sacrifice everything YOU want, to the whims of a 'body' , somewhere else, for a piece of paper.

Put in the stove.
 
thats a fair point GTT, but lets not kid ourselves that a "passive" house is one that is not certified.

There most certainly is a point at which "passive" houses become expensive to build due to teh bells and whistles approach to solving energy usage issues, but to truely have a passive house you must have it certifed. this certification includes a data logging timeframe afterwards to prove its credentials.

Otherwise its entitled a low energy build... which is noble in itself.
 
It is perfectly possible to have a chimney in a passive house.

This one as it says is being built in conjunction with the PHI.
[broken link removed]

It has 2 chimneys. 1 inside the body, 1 outside.

Both were built using traditional masonry.

The internal one was built with an adapted detail using insulating blocks where it bridges the airtightness\insulation layer in the roof.

The flue also contains 2 valves even though a room sealed is specified. There is no such thing as a truly airtight stove apparently. 1 of the valves is on the air source pipe for the stove, the 2nd in the chimney itself close to the insulation layer.

This chimney is so well designed that it is not considered a cold bridge in the PHPP.

It is easier to detail the chimney (thermally) if it is outside the body of the house. This can introduce structural issues depending on your build method.

If the company that did your PHPP knows what they are doing they should be able to provide a detail.

Very best of luck to you.
 
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Thanks SAS, good answer.
I'm trying to get my head around how the valves work in the flue.
Obviously the valves open when the fire is on, and close when there is no fire on

Are the valves automatic, or do they need opening manually when a fire is lit, and closed manually when there is no fire. It might sound like a stupid question.
 
LouisCribben said:
Thanks SAS, good answer.
I'm trying to get my head around how the valves work in the flue.
Obviously the valves open when the fire is on, and close when there is no fire on

Are the valves automatic, or do they need opening manually when a fire is lit, and closed manually when there is no fire. It might sound like a stupid question.
Click to expand...

I'm 99% in that house the pair are going to be wired to a single switch which will be controlled by the occupant as you suggested.
 
sydthebeat said:
thats a fair point GTT, but lets not kid ourselves that a "passive" house is one that is not certified.
Click to expand...

....let us not kid ourselves that a house without a PHI cert isn't passive, either.


sydthebeat said:
....but to truely have a passive house you must have it certifed. this certification includes a data logging timeframe afterwards to prove its credentials.

Otherwise its entitled a low energy build... which is noble in itself.
Click to expand...

I'm afraid I disagree. You truly have a passive house when it performs like one. The presence or absence of a cert will not affect that performance one iota.

Remember: PHI is a commercial organisation, who charge for the service. That your house could meet all the requirements, but that you elect not pay for a PHI cert, does not disqualify you from having a passive house.
 
sydthebeat said:
<snip>But a certificate is proof non occupants that its DOES perform.
Without a cert, wheres the proof?
Click to expand...

Would the heating bills not provide some form of empirical proof.

[this, from a guy who issues certs for a living :)]

ONQ.

PS Not passive house certs, BTW...
 
I'm wading in here. I'm completely with Syd on this and I'm going certified (assuming I can satisfy the criteria).

You won't have heating bills. You will have an ESB bill alright. But most passive houses (even in our milder climate) will have a stove of some sort as a back up and it's not easy to prove how much or little you light it.

Plus there are people that are very warm souls that need a window open at night in order to sleep. There are those that prefer to be able to walk around in our underwear when there's a foot of snow outside. To the former, any house could be warm enough. You see where I'm going.

My biggest fear.... I'm building a house (3256 sq ft) to PHI spec with the target to achieve the certification. However, if I fall short (say 16kw instead of the 15kw target) I don't get the cert but the house will perform like a passive house. The certification has to draw the line somewhere so I don't have an issue with this. If faith should deal us a bad hand 5 years down the line and we were forced to sell, all I really have is a big house that needs a heating system installed from a buyers perspective. I'm actually planning on burying rad pipes in the screed so that should that happen (or if we fall we short of passive) I have a fall back that doesn't involve digging up floors etc to resolve.
 
onq said:
Would the heating bills not provide some form of empirical proof.

[this, from a guy who issues certs for a living :)]

ONQ.

PS Not passive house certs, BTW...
Click to expand...

nope :)

without delving into the murky debate of what is actually 'passive' and what is not...
the consensus is passive houses do not consume more than 15 kwhr/m2 of heating and cooling energy per annum. Your heating bills will not reflect this. If someone has wood fuel for free but needs to burn 30 kgs a day for comfort does that mean its a passive house?

see here for a synopsis
[broken link removed]

Here are the five points that define the current German Passivhaus Standard for Central European Countries:
− Heating criterion: The useful energy demand for space heating does not exceed 15 kWh per m² net habitable floor area per annum.
− Primary energy criterion: The primary energy demand for all energy services, including heating, domestic hot water, auxiliary and household electricity, does not exceed 120 kWh per m² net habitable floor area per annum.
− Air tightness: The building envelope must have a pressurization test result according to EN 13829 of no more than 0.6 h-1.
− Comfort criterion room temperature winter: The operative room temperatures can be kept above 20 °C in winter, using the abovementioned amount of energy.
− All energy demand values are calculated according to the Passive House Planning Package (PHPP) and refer to the net habitable floor area, i.e. the sum of the net floor areas of all habitable rooms.

from: [broken link removed]


once these parameters are met then that house can be said to be 'passive'... if they are not met then the dwelling is simply low energy. The passive house parameters are a method of describing a standard to be met, thats all.
 
So,

If OP would like a chimney then no reason not to have one

unless OP is concerned as to

how many angles can dance on the top of a pin head


Regards

Olddog

( stay real, stay warm )
 
Noob question: How is heat escaping when people enter & exit these passive houses handled?
 
sas said:
I'm wading in here. I'm completely with Syd on this and I'm going certified (assuming I can satisfy the criteria).

You won't have heating bills. You will have an ESB bill alright. But most passive houses (even in our milder climate) will have a stove of some sort as a back up and it's not easy to prove how much or little you light it.

Plus there are people that are very warm souls that need a window open at night in order to sleep. There are those that prefer to be able to walk around in our underwear when there's a foot of snow outside. To the former, any house could be warm enough. You see where I'm going.

My biggest fear.... I'm building a house (3256 sq ft) to PHI spec with the target to achieve the certification. However, if I fall short (say 16kw instead of the 15kw target) I don't get the cert but the house will perform like a passive house. The certification has to draw the line somewhere so I don't have an issue with this. If faith should deal us a bad hand 5 years down the line and we were forced to sell, all I really have is a big house that needs a heating system installed from a buyers perspective. I'm actually planning on burying rad pipes in the screed so that should that happen (or if we fall we short of passive) I have a fall back that doesn't involve digging up floors etc to resolve.
Click to expand...

You are concerned that the house you are building to passive standard may fall short of the standard, i.e. it might use 16kwh/m3 to heat.
Just a question really, shouldn't you know before you start building if the house is going to pass, assuming the Passive House software has been used, and the house is built with good workmanship with all the correct materials.
What can go wrong ? I'd be thinking dont bother putting in pipes under the screed, just get your design and build right !

I'm a bit unclear too about the data logging to prove its passive. Obviously they need to see your electricity bills during the monitoring period......its impossible to tell from an electricity bill what energy was used for heating alone (unless they put a kw/h meter on all heating devices).
Also it would be difficult to monitor how many kw/h came from coal or wood, should the house have a solid fuel unit (not difficult mathematically to work out) but difficult for the passive house people to verify how much wood was burned.
 
I was in a house that was being monitored and the heat recovery unit was switched off,which is bound to have an effect on the reuslts.I was told that they switched it of just before I arrived,that they had been showing another person around and must have forgot to switch it back on.Maybe genuine,but I know another guy who was there on another day and had the exact same story!!
 
LouisCribben said:
its not handled

when the triple glazed argon filled airtight doors are opened, heat will escape.
Click to expand...

Ever heard of draught lobbies??

its completely obvious that the use of the house after will affect the actual performance of the project. Whether or not a build is "passive" means it meets set parameters. These parameters HAVE TO make certain usage assumptions ie a living area constant temp of 20 deg etc.

Doors are opened when someone walks through them. This quick temporary action is not going to cause a significant temperature drop throughout the dwelling so as to make the passive heating system useless.

I have heard the same queries about windows "sure, what happens if you open a window".... again the same is applicable. Firstly you need to ask why windows are opened??? in summer it is usually to counteract over heating. This in effect is passive cooling. So when else would you open a window??? to let out smells and water vapour. Both of these issues are dealt with by means of mechanical ventilation with an intelligent control system. there will be facility for rapid exhaust of air from rooms with steam or smells....

so when else would you open a window for a length of time that would affect internal temperatures????

A sense of reality needs to be maintained ... !!
 
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