Replies

1. GBA Editor
   Brian Pontolilo | Jun 07, 2019 09:49am | #1

   Krohner,

   If the make up air was only serving the boiler, then I don't see any reason to keep it. Same with the chimney, of course. What to do now depends on how involved you want to get. You could cut the pipes near the wall and roof inside, removing the long runs, cap or plug what's left, and seal this quick fix with canned spray foam. From the exterior, it would continue to look as it does now. Or, you can remove them and fix the siding or trim where the intake is located and patch the roofing. I've been in similar situations and have generally left things in place, assuming that eventually the house will be resided or reroofed and that would be a better time to remove the penetrations. As long as you seal them up one way or another, I think it is personal preference.

1. 
   Krohner | Jun 07, 2019 01:29pm | #5

   Thanks,
   The air make up is under our desk which sits about 2 ft off the ground, and actual goes through the ledger board for our deck. It has the standard metal grate to keep critters out. Was kind of wondering if I should put some water sealing tape over the grate before filling it with spray foam. It does have a hood so I think is should be ok either way, but not sure what the best practice is.

2. Expert Member
   Dana Dorsett | Jun 07, 2019 11:55am | #2

   Sometimes make up air vent holes are in a convenient location and size for installing a ductless heat recovery ventilator, which is something to consider.

   With the chimney it's best to brick up the port. If the flue is completely abandoned capping it at the top to prevent rain/snow from gaining entry is also a good idea. Using a masonry sealer on any exterior exposed brick can sometimes be important too- most brick is pretty porous, with a strong capillary draw, and without the heat to drive off the moisture it can become a path for moisture into your house.

   I presume you've done a Manual-J or fuel use load calculation to properly size the new boiler? If not, take 15-30 minutes to at least run the fuel-use load numbers as a sanity check:

   https://www.greenbuildingadvisor.com/article/out-with-the-old-in-with-the-new

   If the new boiler is a modulating condensing boiler, run the napkin math on the zone radiation too. Bigger is the opposite of better when it comes to mod-cons- it needs to be right sized for the radiation to get condensing efficiency out of it without short-cycling it into an early grave:

   https://www.greenbuildingadvisor.com/article/sizing-a-modulating-condensing-boiler

1. 
   Krohner | Jun 07, 2019 01:49pm | #6

   Thanks, I will look at the ventilator idea.

   The chimney is a class 2 without any brick.

   It is actually a variable speed GSHP. So the manual J stuff definitely applies. We've done the zone by Zone manual J and even ran an accidental test at low temperature last winter. We had dual fuel electric boiler and a propane boiler. The electric boiler had 3 out of the 4 elements burn out and was only drawing 1/5th of the normal kW (putting that smart meter to use). So we were initially unaware that we were running more on our propane boiler until it ran out in late December during a cold snap. With circulating temperature at only 90 deg f we were able to maintain 60 deg in the house.

1. Expert Member
   Dana Dorsett | Jun 07, 2019 02:26pm | #7

   >"It is actually a variable speed GSHP. So the manual J stuff definitely applies."

   Indeed the load calculations DO apply. At the comparatively high upfront cost of a GSHP over sizing gets to be pretty expensive!

   At the high cost of heating propane & resistance electricity it's pretty easy to rationalize going with GSHP, especially when there are sizable tax incentives in place. With a competent designer and installer it will run as efficiently as a ductless mini-split (or better), and should last longer too.

3. 
   Jon_R | Jun 07, 2019 12:43pm | #3

   I'm curious what this new boiler is that doesn't need venting - electric?

1. 
   Krohner | Jun 07, 2019 01:20pm | #4

   I avoided mentioning that it is a GSHP, because I know there are some strong opinions on them. But in our case is should be about a 5 year payback.