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Direct Air vs Air from Room - for Wood stove. What's best for high humidity house?

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2 hours ago, Woodworks said:

But it's say 20c cooler but it's going to heated to 350c plus. Cant see that will make much difference

There may be good reasons for going room sealed, one of them may be that the house is designed to be nearly airtight  with very low infiltration rates with a whole house ventilation system managing the air changes. This could affect the operation of a stove when the pressure in the house changes. After all we are only talking about  fractions of an inch water gauge  between the stove and the top of the chimney, this is what drives the air through a natural draught (i.e. no fans) stove.

 

As I tried to point out earlier in the thread the actual air flow through a small stove is likely to be a small part of the air changes needed in a house for a healthy atmosphere.

 

Typically a stove will take ambient air from a room at about 20C raise it to about 800C to ensure a clean burn and exhausting it up the flue at about 200C, the idea being that it leaves the top of the chimney at above 100C to avoid condensation in the chimney.

 

Heat losses due to dumping 20m3/hour of air with a delta C of 80 to 180 is in the order of 1kW and is not significantly different for room sealed or normal stoves. A gas boiler has much lower losses.

 

@Retired Climber gets my point that increased air density leading to increased massflow is a consideration for a heat engine but not for a simple stove.

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4 minutes ago, Stubby said:

Ok . Just a thought . Room seal kits to pipe air directly to the stove from out side ( without the cold air being in the room ) I thought was a good idea that's all .

It can be @Stubby but not for the reason you thought. All modern domestic gas boilers are room sealed.

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1 minute ago, openspaceman said:

It can be @Stubby but not for the reason you thought. All modern domestic gas boilers are room sealed.

Hence the Doh ! I presume 🙂

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20 minutes ago, Stubby said:

Hence the Doh ! I presume 🙂

Yes it was the problem of  some knowledge of engines leading to an assumption about stoves and that I thought we had discussed this before, not more than that.

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1 hour ago, openspaceman said:

Yes it was the problem of  some knowledge of engines leading to an assumption about stoves and that I thought we had discussed this before, not more than that.

Yes , sorry we probably have . I have been wrong before and I expect I will be wrong in the future bud ! 🙂

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24 minutes ago, Stubby said:

Yes , sorry we probably have . I have been wrong before and I expect I will be wrong in the future bud ! 🙂

Careful mate you'll be getting as paranoid as I 🙂

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We live in a similarly damp (70-80% humidity, lots of condensation), old, stone Welsh house by a stream. Two woodburners, one 5kw in the living room which sucks from the room, and a bigger 8kw ish in the kitchen with direct air (not room sealed, I can feel a draught coming into the room from the air inlet to the stove!). Overall, the kitchen is drier - but it's not a fair comparison, as the kitchen is more modern, draughtier, used more and further from the stream! Only 10m or so, but that may be enough to make a difference?

 

Looked at PVI / MVHR type stuff, but the chap we had out to quote was a bit too glib and salesman-y, I wasn't convinced it would work in our big, old, draughty house. I bought a window / water vacuum instead, which does a good job of removing the condensation.

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Would it be good or bad to take a reasonable sized pipe into the roof space to draw air from there?  Warmer air and venting the roof space at the same time??

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4 hours ago, Billhook said:

Would it be good or bad to take a reasonable sized pipe into the roof space to draw air from there?  Warmer air and venting the roof space at the same time??

The roof space in a well insulated roof should be near ambient air but yes whole house ventilation units are often in the loft but vent directly to the outside because of condensation risk.

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