Can I insulate the b-vent pipe in my attic?

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#1

Originally Posted By: chanmouli
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Hello Friends,


My attic is too cold and more condensation occurs in the b-vent pipe in the attic and it leaks water in attic as well as in the basement(bottom of the vent pipe). we collect like a full cup of water in the basement during very cold days.


Can I add insulation to the b-vent pipe in the attic so that it prevents the condensation? If so, please recommend the proper insulation methods and materials for the b-vent pipe.


Any help is appreciated. Thanks a lot.

#2

Originally Posted By: dvalley
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Welcome to NACHI.


1st - Don't insulate the B-vent, this vent has a barrier (second layer) for a reason. It's already insulated.

2nd - How much insulation (inches) do you have in the attic and what type of insulation is it?

3rd - Is the insulation on the floor of the attic or the ceiling?

4th - What types of venting do you have installed for your attic cavity?

Answering these questions will give us a starting point.

--
David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

#3

Originally Posted By: chanmouli
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Thanks a lot.


2. Approx. 12 inches of fiberglass loose fill insulation.

3. The insulation is at the floor, no ceiling insulation.

4. soffit vents & ridge vents

Please, let me know if you nee any other information.

Thanks again for youe help.

#4

Originally Posted By: dvalley
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Everything in the attic appears fine so far but I have more questions?


Are all the soffit vents unblocked from the loose fill insulation or are there baffles installed at this soffit area to allow outside air to enter?

What type of heating unit are you venting? Is it oil or gas? And how many floors is this vent going through?

Did you change your heating unit from a low/mid efficiency to a high efficiency? Low efficiency gas appliances such as older 78 percent AFUE furnaces/boilers rarely have such a condensate problem because the flue gas exits with a relatively high temperature making condensation difficult to occur. However, in your situation it sounds like you have a unit with efficiency just below 83% and the flue gas exits much cooler. These are known as category 1 type gas appliances and they are much more prone to developing unwanted condensation on B-vents.

This could also be caused from an excessive number of elbows installed. Can you figure out how many elbows are being utilized to vent this unit to the outside, from bsmt to attic? There should be no more than two elbows from the heating unit to the attic area.

How much B-vent is penetrating outside the roof surface?

I want to help you resolve your condensation problem but I need more definitive answers.

--
David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

#5

Originally Posted By: chanmouli
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Thanks a lot for your reply.


Yes, baffles are installed at the soffit area.


The heating unit is gas, 10 yrs old, Amana 80% efficiency 67000 BTU.


I have also checked the elbows. There are only 2 elbows from basement to attic.


The vent pipe is penetrating outside for approx. 2 foot(including cap)


When I was outside and looking at the roof to find the size of the pipe thiss morning, I also found out that water is coming out around the flashing on the roof(exterior side).


Please, let me know if you have any more questions.


Thanks again for your time.

#6

Originally Posted By: phinsperger
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chanmouli wrote:
I also found out that water is coming out around the flashing on the roof(exterior side).


Could there be a breach in the flashing that is letting this water come in? From your description there doesn't really sound like a condensation issue.

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#7

Originally Posted By: chanmouli
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We also initially thought that the rain water is coming in. A chimney professional looked at the flashing and he put the sealant on the flashing. But, we are still getting the water. We didn’t have rain in our area for the last one week. But, we are collecting half a cup of water in the basement every night( in the daytime, we don’t collect the water at all. It is happening only during the night time)


Thanks a lot for your time and help. Can I post a picture here so that everyone can get an idea?

#8

Originally Posted By: ssopha
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do post pictures of the problems.

#9

Originally Posted By: dvalley
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A pic will only tell us that its condensating…We believe you.


According to your conditions, everything appears to be to fine. There?s only one last thing ?Is your B-vent insulated? An insulated B-Vent has a 1/2" blanket of fiberglass insulation between the aluminum liner and the galvalume case. This insulation maintains the flue gas temperature over standard air insulated B-Vents. This type of B-Vent is used where runs must be made through cold areas such as in your situation or for longer than average heights above a roof where cold conditions could lead to condensation problems.

--
David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."

#10

Originally Posted By: mrbpsdntx
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Is it possible that the B-vent liner has failed in one of the sections in the attic?


Even tho it has been in service for years, is the size correct? most likely it should be 4 inch vent!


Quote:
INVERSE BEADS add rigidity and ensure proper spacing between the inner liner and the outer wall. The inverse beads also serve to seal the air chamber between the inner and outer walls. As a result, the inner liner heats up rapidly and remains hot during the operation of the appliance, minimizing the effects of condensation.


a lot of good info here!
http://www.duravent.com/docs/instruct/shbook.pdf
#11

Originally Posted By: dvalley
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Quote:
I also found out that water is coming out around the flashing on the roof(exterior side).


If you?ve got condensation signs on your exterior flashing this can be only one last resort. It has to be collecting on the underside of the B-vent hood and dripping down the sides of the vent connectors.

If this is the case, then that tells me that your flue gases are cooling too quickly before they have a chance to vent properly. This situation causes condensation build-up on the underside of the hood. If this is the situation then your vent connectors are too long (termination is too far away from your Amana furnace.)

--
David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."
#12

Originally Posted By: mrbpsdntx
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chanmouli, I think you may be on the right track. It’s a long way from the basement to the roof! Something is letting the flue gas cool to much before it gets to the top. That’s why I was wondering if there is a failure in the liner, or even a seperated joint in the wall, thus letting it cool to soon?

#13

Originally Posted By: chanmouli
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Thank you all for your help.


I am not sure whether it is fiberglass insulated. How can I find that out?


Regarding the termination height, it is as same as my neighbors( similar houses, similar systems).


Is something in the furnace like improper combustion, etc… could cause this situation? This is 10 yrs old system. I bought this home 3months ago. I am not sure when it was serviced last.

#14

Originally Posted By: dvalley
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Tap on the vent connectors. If you hear a thud, its insulated. If you hear a hollow sound, it’s not insulated.

–
David Valley


MAB Member


Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."
#15

Originally Posted By: chanmouli
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I tapped all the vent connectors. A vent connector(approx. 3 ft) in the attic runs at 45 degree angle seems to be single wall, I could hear the hollow sound. Actually, water leaks in this portion of the vent system in the attic. Based on this, Can I insulate that portion of the vent system ? Thanks for your continued support and help to fix this problem for me.

#16

Originally Posted By: dvalley
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Do yourself a favor…don’t start wrapping vents…Have it replaced with an insulated vent connector.

–
David Valley


MAB Member


Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."
#17

Originally Posted By: rsummers
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I would replace the flue with double wall type B vent and check what the blower speed is set at. The installers may have switched the speed taps up to med high to get more air flow. I was always told to keep the temperature rise in the upper 2/3 of its rated temperature rise charts. These can be found on the inside of the doors or in the installers guide. You should just call a pro out depending on how long its been condensation thru the flue the heat exchangers may be rusting out.

#18

Originally Posted By: chanmouli
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David:


I have already spent $350 for the chimney guy to come and put the sealant on the roof flashings and storm collar. I would like to have some temporary solution to run through this season and replacing the vent next season. thanks a lot for helping me to narrow down the problem.


If I want to replace the vent connector, whom I should I call? chimney pro or HVAC pro?


rsummers: Thanks for your valuable suggestion. so, incorrect blower speed would result in condensation?

#19

Originally Posted By: dvalley
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A licensed HVAC tech is recommended, and if condensation was entering the top of your furnace, take Rollands’ advice and have the heat exchanger evaluated while the tech is on site.


Your welcome and Good luck.

--
David Valley
MAB Member

Massachusetts Certified Home Inspections
http://www.masscertified.com

"Some cause happiness wherever they go; others, whenever they go."