High Performance Home with fireplace issue

[Lloyd H]

I have a homeowner with a problem when burning his fireplaces with the doors open. The fireplace does not smoke at the opening, but odors are being drawn in at the conditioned attic. The house is tight, although no blower door test done.

Some of the odors are smoke related, but the smoke alarms do not go off. Some of the odors are sewer gas. The appear about an hour after the fireplace is used.

I advised the homeowner to open a window when burning the fireplace to see if this eliminates the smells. Assuming it does, is there anything other than opening a window that will work?

[darthvader]

We need more information to help you, Is it a wood fireplace or gas fireplace? if gas is it vented?

[Lloyd H]

It is a wood burning fireplace. One is a factory built unit and one is field built.

[darthvader]

You are very confusing with your plurals. There are two separate fireplaces, do they both vent into same chimney/chase and do they have separate flues?

[Lloyd H]

2 fireplaces. 2 chimneys. Both chimneys inside thermal envelope. Separate locations in house. Both on first floor

[darthvader]

Will either one cause odors in the attic?or is it one specific one that causes the odor? You say the attic is conditioned, I'm assuming it is unfinished and unvented. Are you only smelling it in the attic? How old are the chimneys? have they ever had a chimney fire? If opening a windows doesn't help, it could be cracked flue liners leaking into the attic. You should probably have the chimneys get a level two inspection. If opening the window does help, they need to have fresh air brought in to the fireplaces.

[Lloyd H]

Both create smells. This is a new construction and no more than a few fires built. Both have outside air, with ducts not crushed.
It has been suggested to check for small amounts of smoke escaping from the top of the fireplace opening.
What I suspect is with the doors open there is not enough free air to properly vent the fireplaces.
The question is; if opening the window works, what is the best way to remedy the situation?

[ga-hvac-tech]

Building a house 'tight' is great for lowering heating and cooling costs... however fireplaces that do not draft properly is one of many results of a 'too tight' house. Other issues include a clothes dryer that does not dry well, kitchen hood that does not take out odors, bath vents that do not take out odors and do not lower humidity... See the pattern: not enough air coming in to replace the air going out. In the industry we call this Make Up Air or MUA. Another issue of a 'too thight' house is the air gets 'stale'... which is a health hazard.

Have an energy specialist come out (preferably one that is also a fireplace specialist), and look over the house. I suspect you will find two things:
1) Something wrong with the fireplaces and/or flues
2) House is too tight and needs more MUA
Correct these issues and you will be fine.

As to specifics; well someone needs to be there to inspect the house...

[Lloyd H]

GA-HVAC Tech
Nothing wrong with the flues. I know the house is tight and all that. The question is about solutions. What methods are there to make the open fireplace work with open doors in a tight house, short of opening windows.

By the way there is no such thing as a too tight house. Just improperly vented houses. There are 2 HRVs installed for ventilation and the kitchen hood has an interlinked fresh air vent with damper. The dryer has a boost fan. The baths are naturally vented through the HRVs. The question is how to make the fireplace work.

[ga-hvac-tech]

I already answered your question: Either the fireplaces and/or flues are not right, or there is not enough MUA.

However it seems engineering principles are more important than what works and what does not. If I had a nickel for eery time I have seen this thinking... I could retire.

I will wish you the best of luck...

Let us know what you figure out.

BTW: Behind the Pro door at this forum is a building science forum (for professionals only). If you had access, you would be able to read many a well certified person with years (some decades) of experience--explain that YES, a house CAN be 'too tight'.

[Lloyd H]

I posted here because I was told there was possible resident knowledge here.
I got actual help on the building performance linked in site.
You would do better to spend more time reading about building science, and learn why there is no such thing as a too tight house, than promoting the behind the curtain professionals.
I am an HVAC professional and have been for over 30 years, I just did not bother to take the time or effort to get behind your curtain. Good luck, you should pray more and give advice less.

[teddy bear]

How much fresh air ventilation is provided? I suggest that you have a minimum of a fresh air change in 4-5 hours minimum. This should be fan powered. Bathfans, kitchen hood, and clothes drier may need more. Open combustion devices using gravity chiminies compete with each other and all the power exhaust in the home. Wind also creates negative air pressure that may back draft them.
Consider a whole house ventilating dehumidifier like an Ultra-Aire with a make-up air ventilation option for you fresh make-up air source.
Supplemental humidification and dehumidification may be need depending on the outdoor dew points and the number of occupants in the home.
Regards Ken

[ga-hvac-tech]

I posted here because I was told there was possible resident knowledge here.
I got actual help on the building performance linked in site.
You would do better to spend more time reading about building science, and learn why there is no such thing as a too tight house, than promoting the behind the curtain professionals.
I am an HVAC professional and have been for over 30 years, I just did not bother to take the time or effort to get behind your curtain. Good luck, you should pray more and give advice less.

Please do not take this personally... however someone seems to come along about once a month...

They are always a 'guest'... not a Pro. They seem to think they know more than the PRO's here... and act 'superior'.
They usually leave without much information because of their behavior.

I will stand with my diagnosis in post #8...

Please let us know what you find, and what the solution is.

[darthvader]

...The question is; if opening the window works, what is the best way to remedy the situation?

If the window does the trick you are in need of more fresh air. It's quite possible the fresh air you have brought in isn't enough, and you need another HRV or more depending on how much air you need.
http://www.engineeringtoolbox.com/ai...oom-d_867.html this is pretty good information on air change rates, but you also need to figure if your fresh air that you currently bring into the fireplace is big enough to support your chimney size.
You should also verify that the chimney is built correctly, chimneys are almost never built properly. Building inspectors don't know what they are looking at, and masons don't always know how to build them either.
We are trying to help you, we don't come on these forums just to bash people. Sometimes it come across that way, but try and remember that the forum doesn't convey tone very well.

[David F]

As one of the "new people here" and having been a Licensed Mechanical person in the state of Michigan since 1975, and my father before me, I want everyone to know that I have found over the years that fireplaces can be strange, does not matter who built or how, some just cause problems. So as an answer. Is the chimney high enough ? Have you tried making it higher as a test? Are you in a valley or on a hill ? Near a lake ? Is there a peak that although far away is still higher than the chimney ? Have you tried to preheat the chimneys with the doors closed first and than opened them after the fire is burning good ? And as it has been said even if there is air, well keep checking, and good luck with your project.