1 Helpful?

What should I do to make sure an older boiler is venting properly when I seal up the basement?

I am sealing up the basement of a 100-year old multi-family with a 40+ year-old steam boiler. Prior to this work there was a lot of airflow intrusion which is now being reduced. How do I make sure that the boiler is venting properly up the chimney and there are no internal leaks? Is there anything I can do to introduce heat savings on the venting end of the cycle without changing out the boiler?


Asked by Bob Rueter
Posted Mar 3, 2009 8:53 PM ET


3 Answers

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Atmospherically vented boilers require an adequate amount of combustion air, as you know. Code requirements for combustion makeup air vary depending on whether a home is built to average construction or tight construction — loosly defined terms, unfortunately. An HVAC installer or home-performace contractor should be able to test the operation and safety of your equipment to determine whether adequate combustion makeup air is available. If you can't determine this by yourself, it's time to call a professional.

If combustion is incomplete and venting is imperfect, your boiler could release carbon monoxide into your home. It's not worth guessing on the details.

Answered by Martin Holladay, GBA Advisor
Posted Mar 4, 2009 3:07 PM ET



I have been look at products from this company for my own house: http://fieldcontrols.com/cas.php

I have no idea how well they work, and would rely on expert advice myself. I have heard that there can be problems (particularly at start up) with the boiler pulling in completely un-tempered air.


Answered by Tobias Richon
Posted Mar 5, 2009 11:22 PM ET


The average boiler lasts 30 years. Perhaps a new ModCon boiler with sealed combustion and no more worries.

To make a one hundred year old house tight enough to starve a boiler is very difficult. A combustion analysis by a qualified heating contractor would be wise however.


Answered by Morgan Audetat
Posted May 18, 2009 6:40 PM ET

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