Moisture damage from venting?

Steve Goldstein

I live in an 1868 farmhouse in upstate NY. I had a Baxi Luna HT modulating/condensing boiler put into service yesterday, and it seems to be working nicely.

Here's my question. The flue vent leaves the house near an inside corner. My house's siding is cedar clapboards. I went outside this morning, and the clapboards (especially the clapboards on the wall perpendicular to the wall the vent exits from) are quite wet. The outside temp this morning was in the mid 40s.

I checked the Baxi installation instructions, which say that the vent cannot be less than 6" from an inside corner. This vent is 6-1/2" from the inside corner, so it is installed without violating that spec.

As the homeowner, however, I must be concerned about the long-term health of the house. Will all this moisture (and ice build-up during cold winter months) damage my clapboards (the wood and/or the paint)? If it was a vinyl-sided house, I'd be less concerned. But I know that wood and water don't mix very well....

See attached pics for details.

Brad White_9

Nice looking restoration!

I like that field stone foundation and the "newness" of the siding.

I agree with you re: venting. Manufacturers recommendations are just that, a minimum. Inside corners are tricky because prevailing winds do funny things on both windward and leeward sides of a house and at different times of the year.

I have a corner of my house which is always clear of leaves, the winds scour like a tornado to clear the area by the door. Snow however, drifts there and piles up.

What is the snow drift condition at your vent outlet? That would tell you much, not to mention as a safety check of your distance to grade. You obviously do not want snow blockage and CO back-up into the house.

Going forward, you could either move the vent (last resort but a sure thing).

Second-Tier solution might be to sheathe the sidewall impingement area with a sheet of copper and make it a sculpture of some sort, like you meant it to be and not an afterthought (which it would be at this point

Boilerpro_3

I'd be worried

I have never worked with a BAxi, but I don't know of any other manufacturer that would allow this vent location. Usually minimum space is several feet from an inside corner. Codes may frown upon this too.

Boilerpro

Steve Goldstein

Not concerned about snow drift

Having lived in this house for 10 years now, I'm not concerned about snow drifts. I don't think I've ever seen the snow come up to the clapboards in that corner of the house.

I'm more concerned about moisture and freezing/thawing on the clapboards. I'm wondering if it would be possible to replace the metal 360* vent cover that's installed with some kind of directional vent cover that would point the moisture down toward the ground....

Brad White_9

I agree with Boilerpro

and should have commented on the distance requirement. Viessmann (Vitodens) for example has a 36 inch requirement from an inside corner.

Agreed you are not concerned about drifting snow but that would be my first concern so had to mention it. (You will not die from peeling paint, even if it is lead paint...)

But yes I agree with you, Steve, that you are likely to be re-painting there unless you do something.

Are you sure it was not 6 feet clearance or a typo? I would think any manufacturer would be more conservative than 6 inches....

Steve Goldstein

What was that link again?

Someone posted a web link a while back where you could download the installation instructions for different boiler manufacturers' products.

Does anyone have that link? I'll download the Baxi manual and confirm the 6" vs 6' thingy.

Steve Goldstein

I found it and 6\" is correct

Here's an image from the Baxi installation manual. Look at line "G" in the table. 6" is the spec, so I can't tell the installer that he's out of spec.

Brad White_9

It is Written...

I was not taking issue with that, just hoping it was a typo. Just seems so out of synch with other manufacturers that I had to ask....

Constantin

Hmmm...

as a fellow homeowner who just finished his (hopefully last) restoration project, I can sympathize with your concerns. I don't consider the location ideal either.

On the other hand, consider a couple of things... clapboard is expected to get wet from time to time... and as long as the ice doesn't adhere all winter long, it's perhaps unlikely to seep in and cause damage. You could monitor the situation with a wood moisture meter. That would tell you in a heartbeat how the wood is doing near the outlet vs. elsewhere on that wall.

Lastly, if you find that the wood is absorbing a lot of moisture (which I presume would happen more in the summer than the winter months), then I see three options open to you:

• move the outlet
  
• modify the outlet
  
• change the clapboard to something impervious like HardiPlank with some ice and water shield underneath

Steve Goldstein_2

modification plan

I've discussed my concerns with the contractor. What he's going to do first is wrap a small piece of stainless steel sheeting on the side of the outlet that faces the perpendicular wall, to direct the moisture away from that wall. Perhaps I'll post a pic after he's done.

Brad White_51

That seems like

a prudent course of action. Constantin's point about wood eexpecting to be wet is a good measure of common sense. I would add that the condensation is acidic (hey so is Cedar!) but it bears monitoring.

Dave Stroman

I wonder if the manual should say 6' instead of 6".

Dave in Denver

Brad White_51

Exactly.

Just *has* to be a mis-print. In this age of liability and beind super-conservative, why would a manufacturer stick their neck out like that.

Constantin

Heh...

... LOL ...

Once upon a time, I spent far too much time with a large blower in the hills of TN developing a outdoor gas water heater. Back then I learned the meaning of developing a geometry that would allow for no ΔP between the intake and the exhaust... without the benefits of CFD modeling... took a while.

Given that this exhaust does not strike me as particularly innovative in its shape, I think you're probably right, a misprint is the most likely explanation.