Question about firebox and flue gasses and particulates

[Highbeam]

Good points. Can you give examples of high efficiency and low emissions wood stoves? Would England's Stove Works' "Madison" (models 15-SSW01, 50-SHSSW01, and 50-TRSSW01) qualify? It's rated at 72% HHV (78% LHV) , with 1.9 grams/hour emissions.

Today, you can go to the new epa list to compare emissions and efficiency. The englander is not high efficiency or low emissions! It’s cheap though.

 

[Mech e]

Our friend's medical conditions aren't respiratory or allergen related. As I understand it, they are genetically-inherited immune system issues. For some reason combustion byproducts cause the immune system to malfunction.

Okay, understood. I would then have the furnace checked by a qualified technician. They should not be getting any combustion gasses into the house. If they are, the system may have a cracked heat exchanger.

 

[habanero]

Yes, but a specific type that recovers latent as well as sensible heat. That style recovers moisture in the air so it does not dry out the interior air as much. This style does not work well in below freezing climates.

Thanks for the info. I'd imagine in your part of the country there aren't many ERVs installed? Our winters are fairly mild (lows in 30s, occasionally into 20s and teens), so it may work as a heat supplement. Our problem here is summer heat (105-120), but that's another story.

 

[habanero]

Today, you can go to the new epa list to compare emissions and efficiency. The englander is not high efficiency or low emissions! It’s cheap though.

Thanks for suggesting using the EPA site to compare brand/model emissions and efficiency.

 

[peakbagger]

The ERVS used in cold potentially freezing climates are sensible heat exchange only. They are pretty much standard on energy efficient buildings.

 

[habanero]

Okay, understood. I would then have the furnace checked by a qualified technician. They should not be getting any combustion gasses into the house. If they are, the system may have a cracked heat exchanger.

Thanks for the suggestion. They had their system tested and checked a year or so ago. The heat exchanger was a prime suspect, but the HVAC techs said everything was OK.

 

[habanero]

I think all tube style EPA stoves have a glass front door, and in virtue of that glass have 'airwash' flow directed toward that glass. I don't know about the design of cat stoves.

Some stoves (Hearthstone Heritage) also have a side door that is typically used for loading. It is a solid door that has no airwash directed toward it. Our Heritage is a nice stove, and works well, but I wouldn't want to heat 24/7 with it.

Edit to add: the 2020 Heritage is a hybrid (tube+cat), but has the same side door design. Might be a little better for daily heating use with the added cat, but I don't know that anyone here even owns one of these yet.

Thanks for mentioning the "airwash". I've read a number of complaints about front doors warping on relatively new stoves. I'd imagine that could be a serious issue with gasses being directed toward a warped door with an inadequate seal.

Thanks also for mentioning that some manufacturers offer models with side-feed door designs. I'm not sure about our friends, but I've only seen front-feed EPA certified stoves.

What is it about your Hearthstone Heritage stove that makes you reluctant to use it 24/7? Nice looking stove.

 

[SpaceBus]

Wood stoves do not release combustion products into the house during normal operation. The whole stove is under negative pressure, which means any openings let air in rather than out. Both of my stoves load through the front door and my freestanding EPA approved unit rarely releases smoke or even any odors into the house. The wood cooker is a bit more temperamental, but that's due to the exterior chimney.

Clearly there is something in the house, combustion product or not, that is causing issues with the current HVAC setup. I understand that the home and system have been inspected, but perhaps a second opinion is warranted. Our house was inspected five times prior to purchase but I still had to replace a lot of structural framing. There might be a vector that hasn't been considered; a hidden leak creating mold, rodents, or something else entirely. The family may not have typical allergies, but mouse feces or mold spores can really cause some issues nonetheless.

 

[habanero]

The ERVS used in cold potentially freezing climates are sensible heat exchange only. They are pretty much standard on energy efficient buildings.

Thanks for the info. Have you ever worked or lived in a building with an ERV/HRV installed? I haven't, and have wondered how "stuff" in the outdoor air is addressed, whether it's allergens, particulates or gasses. I'm guessing HEPA filters would take care of most particulates, but gasses would probably be a trick to eliminate.

 

[Socratic Monologue]

Thanks for mentioning the "airwash". I've read a number of complaints about front doors warping on relatively new stoves. I'd imagine that could be a serious issue with gasses being directed toward a warped door with an inadequate seal.

Thanks also for mentioning that some manufacturers offer models with side-feed door designs. I'm not sure about our friends, but I've only seen front-feed EPA certified stoves.

What is it about your Hearthstone Heritage stove that makes you reluctant to use it 24/7? Nice looking stove.

I'm not sure about the warping issues; there are some low-end stoves out there, I suppose.

The Heritage (and many tube stoves/furnaces) is best suited for shorter burns, or frequent attention. They burn hot and fast, relatively speaking, and don't have burn times that are long enough for most people to run the stove around the clock. Having coals left after eight hours in the Heritage is not routine, and not easy to accomplish without practice and skill. It would heat the house great, but it would be a full time job tending it.

I'll also repeat what's been repeated: if my LP furnace was letting 'combustion byproducts' into my family's breathing air, I would cut the gas to that furnace permanently and without hesitation.

 

[habanero]

Wood stoves do not release combustion products into the house during normal operation. The whole stove is under negative pressure, which means any openings let air in rather than out. Both of my stoves load through the front door and my freestanding EPA approved unit rarely releases smoke or even any odors into the house. The wood cooker is a bit more temperamental, but that's due to the exterior chimney.

Clearly there is something in the house, combustion product or not, that is causing issues with the current HVAC setup. I understand that the home and system have been inspected, but perhaps a second opinion is warranted. Our house was inspected five times prior to purchase but I still had to replace a lot of structural framing. There might be a vector that hasn't been considered; a hidden leak creating mold, rodents, or something else entirely. The family may not have typical allergies, but mouse feces or mold spores can really cause some issues nonetheless.

Thanks for the feedback on your freestanding EPA unit. Does a Morso 2b Classic have an "air wash" across the front glass? Sounds like you have reliable draft up the flue of your wood heater. Do you ever have problems with inadequate draft due to high winds? Or extreme outdoor temperatures?

Our friends' issues aren't limited to their house; same symptoms occur when visiting, for example, a commercial building heated with natural or LP gas. Or a commercial building which powers refrigeration units with natural gas. And no symptoms in their home when the gas heat isn't running. Their home AC uses the same duct work as the heater and doesn't trigger symptoms.

I'm not sure how many inspections of their HVAC system or home they've had. I'll pass your "second opinion" suggestion on to them.

 

[Mech e]

Not sure where in California you are, but since the AC is not causing issues, perhaps a heat pump is an option. You mentioned how scorching hot it can get, so heating costs with a heat pump may be comparable. Just need to size the unit properly so the secondaries don't kick in when the temps fall to the lower end of the range for their area.

 

[bholler]

I'm not sure about the warping issues; there are some low-end stoves out there, I suppose.

The Heritage (and many tube stoves/furnaces) is best suited for shorter burns, or frequent attention. They burn hot and fast, relatively speaking, and don't have burn times that are long enough for most people to run the stove around the clock. Having coals left after eight hours in the Heritage is not routine, and not easy to accomplish without practice and skill. It would heat the house great, but it would be a full time job tending it.

I'll also repeat what's been repeated: if my LP furnace was letting 'combustion byproducts' into my family's breathing air, I would cut the gas to that furnace permanently and without hesitation.

There are many tube stoves out there that easily go past 8 hours burns and tons of us easily heat around the clock with them. And no most of them don't put smoke in the house at all. That is an install problem if it is happening.

 

[habanero]

I'm not sure about the warping issues; there are some low-end stoves out there, I suppose.

The Heritage (and many tube stoves/furnaces) is best suited for shorter burns, or frequent attention. They burn hot and fast, relatively speaking, and don't have burn times that are long enough for most people to run the stove around the clock. Having coals left after eight hours in the Heritage is not routine, and not easy to accomplish without practice and skill. It would heat the house great, but it would be a full time job tending it.

I'll also repeat what's been repeated: if my LP furnace was letting 'combustion byproducts' into my family's breathing air, I would cut the gas to that furnace permanently and without hesitation.

Thanks for the explanation on the non-cat stoves. Constant firebox tending is definitely worth avoiding.

From what they've told me, the level of "combustion byproducts" that cause problems for our friends are well below the levels considered safe by industry and government. They have the same symptoms in their home (or in most buildings...including my home... for that matter) during wildfire season from wildfire smoke. They have the same reaction in their doctor's office and in the hospital, if the gas heaters are in operation. As it's been explained to me, the problem isn't that there are dangerous levels of "combustion byproducts" in their home, but that their immune systems have bizarre reactions to something in the byproducts. As I said earlier, it's a rare, odd condition.

 

[peakbagger]

Thanks for the info. Have you ever worked or lived in a building with an ERV/HRV installed? I haven't, and have wondered how "stuff" in the outdoor air is addressed, whether it's allergens, particulates or gasses. I'm guessing HEPA filters would take care of most particulates, but gasses would probably be a trick to eliminate.

I do not have an ERV but probably should. I know a few folks with them and they work well but in very cold conditions they usually need an electric duct heater to get the outdoor air up to acceptable temp as the heat exchangers are not 100% efficient. Many of the new super energy efficient homes need them as the indoor air quality can be poor. I also have run into a few on homes with radon issues. Subslab depressurization and air washing well water are the first steps but radon can also be released by concrete so they use the ERVs so pull in fresh air.

Its tough to design a system unless the specific allergens or contaminants are known. I on occasion need to mess with hospital operating room HVAC systems which use 100% outdoor air. The assumption is the outdoor air is less contaminated than the indoor air. All air runs through prefilters, then HEPA filters, then an ultraviolet sterilizer. The air is cooled and then humidified with steam. They are complex systems and expensive to run. I also used to work in a pulp mill, the outdoor and indoor air in the process areas was very aggressive, it would corrode electronics in a matter of days. The plant was heavily automated so we had local electronic rooms in the process areas and a central control room loaded with industrial PLCs and racks of input output cards. In those areas we sealed the exterior walls of the rooms and then recirculated the air continuously through deep bed activated carbon scrubbers. The activated carbon adsorbs the gases and contaminants so they do not get in the room. The room is also pressurized with outdoor air that is brought in through the carbon filter. The air is also also cooled or heated. The rooms have double super tight doors with special weather stripping but contaminants are always making it in the room so the air flow is continuous through the carbon bed. Expensive to maintain and operate but very effective.

There are professionals that specialize in indoor air quality. They can put in continuous samplers in an area for some period of time and determine the levels of any contaminant. There is also continuous samplers that give real time measurements down into the parts per billion in some cases. The key is if the allergens are known they can measure for them, if they dont know then they have to guess and then a system can be designed to eliminate them.

 

[CincyBurner]

our friend's family has several members with rare/odd medical conditions which are aggravated by a number of things, including combustion byproducts. Their house is currently heated by an LP-gas-fired, forced air system. Unfortunately, gas-fired appliances (any gas-fired appliance, not just their HVAC system) trigger significant reactions

Have they considered domestic geothermal, as suggested by EbS-P ? http://www.energyhomes.org/renewable-technology/howgeoworks.html
https://www.renewableenergyworld.com/2016/02/24/the-hidden-genius-of-geothermal-hvac-systems/
Not sure what the ROI would be.
Lots of heat in the ground. But it's run through a heat exchanger (heat pump), so if ductwork is the underlying allergen issue, then it wouldn't address that.

 

[SpaceBus]

Sounds like a heat pump with a wood stove for the coldest nights is a good compromise. The heat pump will be inexpensive to operate and provide AC in the summer.

The 2b Classic is a modern EPA approved solid fuel heater with an air wash over the glass. It actually has a flap inside the door that actually does most of the work keeping the smoke from coming in. If I'm foolish on a reload smoke will roll out and I've had the draft momentarily reverse on rare occasions when lighting a cold stove during a fall windstorm. This stove is actually extremely easy to operate and live with.

 

[bholler]

Thanks for the explanation on the non-cat stoves. Constant firebox tending is definitely worth avoiding.

From what they've told me, the level of "combustion byproducts" that cause problems for our friends are well below the levels considered safe by industry and government. They have the same symptoms in their home (or in most buildings...including my home... for that matter) during wildfire season from wildfire smoke. They have the same reaction in their doctor's office and in the hospital, if the gas heaters are in operation. As it's been explained to me, the problem isn't that there are dangerous levels of "combustion byproducts" in their home, but that their immune systems have bizarre reactions to something in the byproducts. As I said earlier, it's a rare, odd condition.

There is no constant firebox tending with most bobcat stoves. Yes cat stoves will burn longer. But if you read through many of the cat stove threads here and elsewhere smoke or creosote smell is a common complaint with them.

 

[Highbeam]

I think we need to step back and look at the problem we’re trying solve. These people have some ultra sensitivity to an unknown thing in the air. We’re never going to solve this problem. A freaking hospital is too unclean for them. Since both of them have this problem I’m hoping that some mental evaluations have been made.

Then, if the drugs don’t work, we would start with environment like removing all carpet, pets, cooking, cleaning chemicals, furniture with cloth, etc. to make a clean house. Especially bedding can be horrible.

This home almost requires ductwork heating for the plethora of filtration and conditioning for the air. Electric elements in that ducting or a heat exchanger fed by heated water or refrigerant is the only way to go.

No solid fuel burning heating system in the home will be sanitary enough. Going down this road is just a waste of time and money.

 

[bholler]

I think we need to step back and look at the problem we’re trying solve. These people have some ultra sensitivity to an unknown thing in the air. We’re never going to solve this problem. A freaking hospital is too unclean for them. Since both of them have this problem I’m hoping that some mental evaluations have been made.

Then, if the drugs don’t work, we would start with environment like removing all carpet, pets, cooking, cleaning chemicals, furniture with cloth, etc. to make a clean house. Especially bedding can be horrible.

This home almost requires ductwork heating for the plethora of filtration and conditioning for the air. Electric elements in that ducting or a heat exchanger fed by heated water or refrigerant is the only way to go.

No solid fuel burning heating system in the home will be sanitary enough. Going down this road is just a waste of time and money.

Well said

 

[Socratic Monologue]

Looks like such conditions are accepted as real, but it also looks as if the causes are unknown:

The Chemical Sensitivity Foundation - Heating Systems and Gas Stoves

I'm skeptical -- simply based on the fact (I take this to be uncontested) that the combustion in a condensing gas furnace may as well be taking place on Mars since it is 100% insulated from the indoor air of the space it is heating -- that 'combustion byproducts' are the issue. Sounds as if it could be anything.

The OP is convinced that the problem manifests in spaces with gas forced air heat, and not in spaces heated by wood. Whatever the cause, wood heat is apparently a solution.

 

[SpaceBus]

I think the combustion byproducts can be brought into the home quite easily in a drafty house. Usually these direct vent appliances exhaust at adult human chest or head level if on the ground floor. About the same level as most windows and other envelope penetrations. The combustion is not practically the same as happening on Mars since houses are not air tight and the vent exits in the same vicinity of the remainder of the makeup air required by the house irrelevant of heat source. The wood stoves likely don't cause as much of an issue because the flues are usually much higher than ground level.

Think about the topic assuming the people have a real issue. I was medically retired from the army for a similar reason.

 

[habanero]

Not sure where in California you are, but since the AC is not causing issues, perhaps a heat pump is an option. You mentioned how scorching hot it can get, so heating costs with a heat pump may be comparable. Just need to size the unit properly so the secondaries don't kick in when the temps fall to the lower end of the range for their area.

Thanks for suggesting a heat pump. Prompted me to talk with another friend who had an all-electric mini-split system installed about 18 months ago. The family mentioned in the OP is going to talk with the friend with the mini-split system.

 

[habanero]

I do not have an ERV but probably should. I know a few folks with them and they work well but in very cold conditions they usually need an electric duct heater to get the outdoor air up to acceptable temp as the heat exchangers are not 100% efficient. Many of the new super energy efficient homes need them as the indoor air quality can be poor. I also have run into a few on homes with radon issues. Subslab depressurization and air washing well water are the first steps but radon can also be released by concrete so they use the ERVs so pull in fresh air.

Its tough to design a system unless the specific allergens or contaminants are known. I on occasion need to mess with hospital operating room HVAC systems which use 100% outdoor air. The assumption is the outdoor air is less contaminated than the indoor air. All air runs through prefilters, then HEPA filters, then an ultraviolet sterilizer. The air is cooled and then humidified with steam. They are complex systems and expensive to run. I also used to work in a pulp mill, the outdoor and indoor air in the process areas was very aggressive, it would corrode electronics in a matter of days. The plant was heavily automated so we had local electronic rooms in the process areas and a central control room loaded with industrial PLCs and racks of input output cards. In those areas we sealed the exterior walls of the rooms and then recirculated the air continuously through deep bed activated carbon scrubbers. The activated carbon adsorbs the gases and contaminants so they do not get in the room. The room is also pressurized with outdoor air that is brought in through the carbon filter. The air is also also cooled or heated. The rooms have double super tight doors with special weather stripping but contaminants are always making it in the room so the air flow is continuous through the carbon bed. Expensive to maintain and operate but very effective.

There are professionals that specialize in indoor air quality. They can put in continuous samplers in an area for some period of time and determine the levels of any contaminant. There is also continuous samplers that give real time measurements down into the parts per billion in some cases. The key is if the allergens are known they can measure for them, if they dont know then they have to guess and then a system can be designed to eliminate them.

Thanks for the detailed answer to my question about ERV/HRV. Sounds like you've been able to work on some interesting projects.

I passed your info on to our friends today. They said they'd looked into residential-grade ERVs a few years ago. The problem they encountered wasn't with the core energy exchange technology but the fact that, as you said, "The assumption is the outdoor air is less contaminated than the indoor air." That often isn't the case in our area, particularly during wildfire season. While the ERV and installation were affordable, an adequate filtration system capable of removing the usual particulates as well as problem constituents, such as "light gases" like formaldehyde, made the overall cost too great.

 

[habanero]

Have they considered domestic geothermal, as suggested by EbS-P ? http://www.energyhomes.org/renewable-technology/howgeoworks.html
https://www.renewableenergyworld.com/2016/02/24/the-hidden-genius-of-geothermal-hvac-systems/
Not sure what the ROI would be.
Lots of heat in the ground. But it's run through a heat exchanger (heat pump), so if ductwork is the underlying allergen issue, then it wouldn't address that.

Thanks for the suggestion and the links. I'll pass the info on to our friends.