HRV and me - necessary in old double brick home?

[John McCrae]

First post for me, though I have been reading the forums for the past year, and it definitely helped with my purchase decision.

We just completed an addition, and had a wood stove (Morso 6148) installed by a WETT certified installer.
This is in a house that added 800 sq ft on two floors to a 1400 sq ft double brick pre-1900 home in Ontario, Canada.

Now that the final inspection is required to operate the stove, the local building department is requiring a Heat Recovery Ventilation (HRV) system to be installed in order to pass inspection.

That they didn't make this clear when the duct work was being done and the wood stove was in the plans has me cheesed, but I get the sense they know as much about wood burning stoves as me (that is to say, not a lot).

What I'd like to find out here is: 1. does anyone have experience bypassing the requirement to install HRV by way of a blower-door test or some other means?

2. Is my house likely to be too leaky in terms of natural ventilation to benefit from mechanical ventilation? There's still over half the surface area of the home that has no insulation.

3. What would you do now if you were in my situation? I'm trying to determine if there's a case to appeal this. And along with this, they've issued an "order to comply" meaning the wood stove would need to be removed if I can't get it to comply within their imposed time frame.

The attached image has the wording of the inspection requirements, and the referenced clause is pasted below:

9.32.3.8. Protection Against Depressurization

(1) When determining the need to provide protection against depressurization, consideration must be given to,

(a) whether the presence of soil gas is deemed to be a problem, and

(b) the presence of solid fuel-fired combustion appliances.

(2) Where a solid fuel-fired combustion appliance is installed, the ventilation system shall include a heat recovery ventilator that is designed to operate so that the flow of exhaust air does not exceed the flow of intake air in any operating mode, and that complies with the requirements of Article 9.32.3.11.
​

Have at it! And thanks for any thoughts you can share on this issue.

Oh, one other piece of information is that our home has a ground-loop geothermal system with forced air as its primary heating source, with no natural gas to the house. The stove is there mostly to provide top-up heat and enjoyment in the living space.

- John

 

[begreen]

Did you discuss an outside air supply for the stove with the seller, installer or inspector? I would think that would make this point moot. An HRV is not the only solution.

 

[John McCrae]

Did you discuss an outside air supply for the stove with the seller, installer or inspector? I would think that would make this point moot.

No, I had no discussions with any of them on outside air supply. There was a note on a previous inspection report stating, under notes for proposed wood stove: ". HVAC system requirements shall comply to revised permit conditions." That's it.

 

[begreen]

I believe this stove is mobile home approved. This type of installation has stricter guidelines, one of which is outside air. With an outside air supply there is no risk of depleting interior air supply. I t supplies the stove with outside air for combustion.

I would call the stove seller first and discuss so that you are well informed with the options. Ask if they have run into this before. Then call the inspector's office if an alternative if feasible and preferable.

 

[John McCrae]

Thanks @begreen - I am looking into whether Morso's optional "outside air kit" can be installed to meet the building department's requirements, foregoing the HRV.

On the website www.stovesonline.co.uk I found this info about outside air for my model: "Optional direct air kit available. Primary and Secondary direct, it can be made 100% sealed by simply sealing the heat-shield to the back of the stove around where the air spigot is attached."

Under "Direct Air Supply Type" this model is listed as "TOTAL" for what it's worth.

Wouldn't this achieve the same thing as what the HRV would do, address the risk of depressurization?

 

[begreen]

Yes. Read the north american manual for more details on connecting.

 

[sadpanda]

Erm... that inspector is suspect.

Every HRV/ERV I've looked at specifically says it is NOT to be used for makeup air on solid fuel or other combustion devices.

The mfgs do see comfortable using it for exhausting dryers and possibly small externally exhausting range hoods but even then they are cagey about the CFM.

HRV/ERV is really for tight new construction type stuff anyway.

A mobile home style Outside Air Kit is one solution to make the inspector happy. The other solution is a 'near outside' air source which is nothing more then a dedicated vent that brings outside air in near the inlet for the combustion device. If you have radon then that air will have to come from somewhere outside the home. If not, you could in theory pull that air from a vented crawlspace or basement.

There is some debate about the effectiveness of OAK/near outside air but after 2 years of using an insert as the sole source of heat in a leaky house, having a direct OAK will help a ton. Or you could do what I did before the remodel: get a fresh reload nice and hot then walk around perimiter walls with no socks on... Cheaper then renting a FLIR!

 

[maple1]

The inspector has some wires crossed here somehow. I doubt you get an HRV manufacturer to state they are designed for supplying combustion air to a stove.

 

[maple1]

I think he's misinterpreting (2) above. If you have no ventilation system, what follows is not applicable.

 

[John McCrae]

An update on this: only condition left for closing off the permit is the HRV/ERV.
The requirement was added when we applied for a revision to allow a wood stove. (But in fact they didn't have it required in that revision either, acknowledged as an error).

The inspector said that he doesn't have the authority to waive that requirement.

In speaking with an HVAC specialist, he said that HRV would dry the house out more when the Morso is in operation.
And said to make the case to the building department that it is an occasional use unit with effective output of 24000 BTU / hr, which is only half of the geothermal unit's output. As in, it's not a primary heating source.

I don't know, it just seems like if an HVAC guy isn't pushing for it, a WETT certified installer is not pushing for it, and it wasn't in the original requirements for the renovations, then what value is there in adding one for the sake of the wood stove? I'd welcome any thoughts on how best to approach the building department.

 

[John McCrae]

I think he's misinterpreting (2) above. If you have no ventilation system, what follows is not applicable.

Am I misinterpreting, or the inspector? Could you expand on this?

 

[Ludlow]

This is why people get pizzed. More morons with authority.

 

[maple1]

Am I misinterpreting, or the inspector? Could you expand on this?

He is misinterpreting. And that would be my interpretation - what I said.

I.e, if you have no ventilation system, it doesn't matter. If you do have one, it needs to incorporate an HRV.

And no, the wood stove would not be the primary heating. If that is a conceived issue with them. It is only to supplement.

EDIT: Do you have a ventilation system now?

 

[Ludlow]

Combustion air is for combustion. Does an HRV exhaust as much air as it takes in?

 

[maple1]

Yes. If the distribution system is properly designed (balanced).

More on my point about the wording above. Imo it's a 2 stage thing it is trying to say. First, if you have a ventilation system, then it needs an HRV. Second, if the first is so, then the HRV must also be balanced to ensure exhaust is not more than intake. Because if it was, it could negatively effect your stove draft.

It is not trying to simply say that if you have a wood stove then you need an HRV. But the code guy is interpreting it that way.

IMO.

 

[John McCrae]

The only ventilation "system" in the house is roof and soffit vents and outdoor vented bathroom and stove fans.
Nothing like a whole-house fan etc.

 

[maple1]

Is there a definition of 'ventilation system' in the Ontario building code the above stuff came from?

 

[John McCrae]

No, I'm just going by what I know to be there. I can search Ontario code book for ventilation and see what is noted.

 

[maple1]

OK. Some might consider bathroom or stove fans to be a 'ventilation system'. But I am not so sure an HRV can be included in the installation of one of those?

If it was me I would be arguing with them on the angles I mentioned until I was blue in the face. Or have a lawyer do it. The implications of installing/retrofitting an HRV, into a house with no existing ventilation system already in place, can be rather large & expensive. I still maintain they are misinterpreting the code.

I would also maybe search various HRV install instructions about anything related to supplying of combustion air, and see what that says.

Or, likely the first thing I would do is contact/email the provincial building code people, briefly outline the situation, and ask them to explain the meaning of their code wording around this - that shouldn't cost anything and if the response is favourable should be the strongest argument anyone can make.

 

[John McCrae]

OK. Some might consider bathroom or stove fans to be a 'ventilation system'. But I am not so sure an HRV can be included in the installation of one of those?

If it was me I would be arguing with them on the angles I mentioned until I was blue in the face. Or have a lawyer do it. The implications of installing/retrofitting an HRV, into a house with no existing ventilation system already in place, can be rather large & expensive. I still maintain they are misinterpreting the code.

I would also maybe search various HRV install instructions about anything related to supplying of combustion air, and see what that says.

Or, likely the first thing I would do is contact/email the provincial building code people, briefly outline the situation, and ask them to explain the meaning of their code wording around this - that shouldn't cost anything and if the response is favourable should be the strongest argument anyone can make.

Thanks, I really appreciate your thoughts on this. I'm going to try the routes you suggested - I never thought of reaching out to the province but that makes a lot of sense.

 

[John McCrae]

I've done as you suggested @maple1 and contacted the Ontario Building Code office. The gentleman there was helpful, in terms of offering an alternative:

Also, instead of Part 9, your designer could make use of Part 6 design which refers to the CSA F326. The CSA F326 includes provisions to get away from the requirement of the HRV .​

So I took that info to a friend who is a mechanical engineer working on HVAC projects. He said I might not be able to apply that standard he mentioned, partly because the provision requires a calculation where our vented dryer in the house throws everything off. A better alternative than HRV is a make-up air unit. Anyone have experience with products from Thermolec or Electro?

 

[Caydel]

@John McCrae Ok, so first off - that house is likely to be leaky as anything. We just did extensive renovations to my mother's 1860's brick / stone house. We did a *lot* of air sealing, and drastically improved the situation... but there's still a lot of air that makes it in through the exterior walls in places such as between the rafters between the two floors. Even if you don't have a crack anywhere in the mortar between bricks (and it's guaranteed you do), clay bricks and lime mortars are porous enough that there is always some slow air movement (and vapour movement) through them.

What we found regarding building officials is that you need to be working with the right person. They all know code and how it applies to modern built homes. However, you can't apply the current building code (in terms of energy requirements) to an older mass masonry house - if you do, you will literally destroy the masonry over time if you over insulate, vapour seal, and don't allow it to dry to the inside to a degree. If a brick wall can't dry, then freezes, you will get spalling. Not to mention a cold brick wall is a great way to get condensation in your wall cavity, and no amount of impermeable vapour barrier is going to keep your wall cavity dry over the long term.

We were lucky enough to deal with a building official in our Township who had a building science background, and allowed for a bit of compromise.

I'm not sure how you have pursued insulation so far, but depending on where you are and the makeup of your brick, you probably don't want more than R5 or R10 on your exterior walls. Instead of using a 'standard' poly vapour barrier, really consider using a smart vapour barrier like Membrain: https://www.certainteed.com/building-insulation/products/membrain/ - it is designed to become vapour permeable at 60% humidity to allow vapour buildup in the wall cavity to dry to the inside - this will help prevent condensation on your brickwork inside the wall cavity.

All this to say - any modern house these days typically needs an HRV because they are too tight. Yours won't, but you are being directed there because 'that's what it says in the book'.

Feel free to PM me - maybe our experience could be to your benefit!