Rocket Mass Heater or other suggestions

[Sam Knight]

Hello all,
I am looking for a heat source for my workshop. At the moment I am insulating the ceiling and walls. It is approximately 15'x30' in size with a concrete floor and is a separate building from my house. I have been thinking all along that I would be getting a 220v ceiling electric heater and even have the shop wired up to install this unit but...I am concerned about all the sawdust with this heater. Firehazard?
Lately I have been thinking more about getting a wood heater. I have stumbled across one called a Rocket Mass heater. It seems very doable. I have a mig welder so I believe I can make one on the cheap. Also should have an abundant source of fuel for this heater. Is there anyone here that has one or knows of someone that does that can give me advise as to why this is a good or bad option? Also thought of just a potbelly stove. What would be your suggestion? Go with the electric heater or what? Thanks for any advise you can give.
Sam

 

[KenOfCary]

A lot of people have been installing split system heat pumps in their shops. This would give you year round heating and cooling.

No real personal experience with them. I had the luxury of being able to tap into an overhead heat/air vent in my attached garage shop.

 

[NOTW]

Ken, could you elaborate a little by what you mean with tapping into the overhead heat/air vent?

 

[tri4sale]

Ken, could you elaborate a little by what you mean with tapping into the overhead heat/air vent?

I imagine his house's HVAC system had a line running to a room over his garage, and he just added a vent from that line into the garage.

Just need to make sure the house's HVAC system can handle the expanded area that it has to condition now, if not then the system may run more than it should and may have difficulty heating / cooling the rest of the house. Also, when you go to sell a house, an HVAC vent in a garage that is tied to rest of house will usually raise a red flag. Garage HVAC systems are not supposed to be part of a house HVAC system as they have concern that someone will run a car in garage and fumes will get into house.

 

[RayH]

I imagine his house's HVAC system had a line running to a room over his garage, ..... Garage HVAC systems are not supposed to be part of a house HVAC system as they have concern that someone will run a car in garage and fumes will get into house.

My HVAC contractor refused to connect to the house's system. Said it would not pass inspection for the reason cited above. I wound up going with a "through-the-wall" unit like you see in motels. This was several years ago, and a split-system was not offered as an option. Whatever you do, you will find that HVAC in the shop will increase your number of "usable shop" days greatly.

Good Luck,
Ray

 

[KenOfCary]

No threat of running a car in this garage. It does not have car size doors anymore. They were replaced by insulated walls. And 2x4 studs with insulation installed on the outer concrete walls.

Since a picture is worth a few words, here is what I did.

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I used a Dremel Tool to cut a 6" x 6" square hole in the main duct feeding the house and installed a small vent. As leaky as that venting is, I often just close the vent as it gets too hot or cold depending on the season. Now that the room is completely insulated it stays quite toasty in winter and cool in summer.

I replaced the garage doors with insulated walls with a man door and a window in the separate bays. Cars are made to be outdoor animals. I have another exterior garage that also doesn't house any cars. It contains the tractor and tack for the horses. The carport attached to it is where I store lumber.

 

[Rick M]

Seems like a heat pump would be cheaper and you could let it run all the time keeping temperatures above freezing. Although having a wood stove in the shop would be very nice, I'd probably never leave. I have seen rocket stoves and made a temporary one with bricks. The thing with rocket mass stoves is that you need the mass, a large thermal mass which is going to take up a lot of room.

 

[chris_goris]

A lot of people have been installing split system heat pumps in their shops. This would give you year round heating and cooling.

No real personal experience with them. I had the luxury of being able to tap into an overhead heat/air vent in my attached garage shop.

I had gotten quotes for heating /cooling a basement about 1100 sf with a split system, it was around $4500 installed average (3 quotes)

 

[Jeremy Scuteri]

It seems strange to me that you are concerned about an overhead electric heater being a fire hazard, but the next alternative is a DIY system that actually burns wood. It is my understanding that a lot of insurance companies do not allow wood burning stoves in workshops due to the increased risk of fire. This has been the cause of fires for at least a couple NCWW members.

 

[Sam Knight]

It seems strange to me that you are concerned about an overhead electric heater being a fire hazard, but the next alternative is a DIY system that actually burns wood. It is my understanding that a lot of insurance companies do not allow wood burning stoves in workshops due to the increased risk of fire. This has been the cause of fires for at least a couple NCWW members.

I would only run the wood heater when I'm in the shop vs the electric heater is on a thermostat so it would run when I'm not there. But, this is why I ask this question to get pros and cons for this type of heater. My research so far has been nothing but positive for it. Very efficient burning, and I should have an abundant supply of fuel.

 

[Jeremy Scuteri]

You can always put the electric heater on a switch so it is off when you are out of the shop.

 

[danmart77]

Sam
I'm in the same boat. Woodstove, split system, gas line and surface heater etc. The benefit of the new split systems is how efficient they operate and you can opt for manual over-ride features so it doesn't run on a signal if that's what you want. They operate quite well in both modes: cooling and heating.

Woodstove: things have really changed on the WS and insurance companies coverage. Get the straight skinny on that before you install. USAA will not work with wood shop and woodstove. Sad but that is my case. I might add they will work with the "Taylor" type wood heaters. The fire box is away from the building and you can port the heat in with no exposed flames.

Some folks on the site really love the AC in the hot summers. Easy enough to understand that but in my case, I have a long bench outside and I work outside the shop while doing milling type work. This keeps dust down and I do have fresh air. Its not a fine woodworking shop but I getter' done.

Big doors on the ends has been a real bonus running long stuff. The cornice return above the doors keeps light rain out but on the heavy down pours I have to button up.

Hope something here helps
Dan

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[drw]

I have a Mitsubishi split system in my little shop (24x16) and it does a super job of heating and cooling...it is al extremely quite!

 

[CrealBilly]

Sam
I'm in the same boat. Woodstove, split system, gas line and surface heater etc. The benefit of the new split systems is how efficient they operate and you can opt for manual over-ride features so it doesn't run on a signal if that's what you want. They operate quite well in both modes: cooling and heating.

Woodstove: things have really changed on the WS and insurance companies coverage. Get the straight skinny on that before you install. USAA will not work with wood shop and woodstove. Sad but that is my case. I might add they will work with the "Taylor" type wood heaters. The fire box is away from the building and you can port the heat in with no exposed flames.

Some folks on the site really love the AC in the hot summers. Easy enough to understand that but in my case, I have a long bench outside and I work outside the shop while doing milling type work. This keeps dust down and I do have fresh air. Its not a fine woodworking shop but I getter' done.

Big doors on the ends has been a real bonus running long stuff. The cornice return above the doors keeps light rain out but on the heavy down pours I have to button up.

Hope something here helps
Dan

​

Pretty shop Dan

Eustace Conway from turtle island NC on a mountain men show said something like - the best insurance policy is being able to rebuild it yourself - I really admired that. I'm not quoting Eustace because I don't recall his exact words but it was something to that extent.

Speaking of insurance though what is generally accepted for wood fire - a steel roof or asphalt shingles? One would think steel roof but common sense rarely applies to insurance.

Living in southern IL I rarely "need" air conditioning so I could never justify a split system but heat on the other hand is a "must". We do have a lot of what i call "free days" every year - just open the windows and let the fresh air blow through because it's beautiful (not to hot or not to cold) outside. Today is one of those free days, it's 54 and sunny - just beautiful.

When I lived in NC free days were pretty rare due to the humidity. You guys simply have way to much humidity. I remember breaking out in a sweat just walking across the yard. So I would think you guys need AC and dehumidification more than you do heat. I can't ever remember it dropping below 15 in NC and that was at night it would generally warm above freezing during the day following a below freezing night. Those below freezing nights where pretty uncommon too. But 15 was like a record breaker so it was a ultra rare event.

"Any society that will give up a little liberty to gain a little security will deserve neither and lose both" -- Benjamin Franklin

 

[Don Sorensen]

When you said "Rocket Heater" it made me think of the forced air/LP gas combo that I just bought from Northern Tool. It's shaped kind of like a rock engine. Runs on 120vac and same kind of tank as my grill. But it's loud. It warms my 24 x 32 shop just fine in about 20 min. My uninsulated, open ceiling with gable vents shop. I have yet to close it in properly.

 

[Rick M]

A rocket stove is a highly efficient wood fueled cooking stove designed to burn small pieces of wood. They burn very hot and produce very little smoke. The design was meant for third world people who have difficulty finding fuel for their cooking stoves. They are also popular among outdoor enthusiasts and lately I've read of some used as heating stoves. The "mass" part comes from adding a large thermal mass, usually concrete, around the stove pipe to absorb and store heat.

 

[bluchz]

Rocket Mass heaters require a lot of time to heat properly. I built one for a greenhouse and found that a burn to heat the "mass" took at least half a day. The burn requires more attention that an regular fire place. I had to tend it, add or adjust the wood feed, every 20 to 30 minutes. I have a wood stove in my shop and am much happier with it than the RMH. My RMH is a 6" system with a 5' cobb bench It is nice if you are home all weekend and have time to tend it, a good warm bench to sit on and read. I find the wood stove to be more compatible with my weekend shop time.

 

[SubGuy]

Pellet stoves are very efficient heating machines that require little work. If you can insure it, it's pretty much only requires a bag of pellets every so often and a 115 outlet. Had several friends out in WA that had them and I was exceptionally impressed. They heat up fast and the flame is contained inside.

 

[petebucy4638]

Fifteen years ago or so, it was not uncommon to to see garages share the house HVAC system. In some cases, there would just be a supply line and no return air. In others there would be both. Of course the return air line was a significant risk to the occupants because it could pull carbon monoxide into the residence if an automobile, law mower, generator, etc were running in the garage. In later years code would not permit a garage to share the same HVAC equipment as the home.

I know several small shop users who have installed window/wall heat-pumps in their shop/garages. They are reasonably efficient, inexpensive and very simple to install. A heat-pump is more efficient than resistance heat and it also give you the opportunity to cool the garage in the summer along with reducing humidity.

I imagine his house's HVAC system had a line running to a room over his garage, and he just added a vent from that line into the garage.

Just need to make sure the house's HVAC system can handle the expanded area that it has to condition now, if not then the system may run more than it should and may have difficulty heating / cooling the rest of the house. Also, when you go to sell a house, an HVAC vent in a garage that is tied to rest of house will usually raise a red flag. Garage HVAC systems are not supposed to be part of a house HVAC system as they have concern that someone will run a car in garage and fumes will get into house.

 

[Jeremy Scuteri]

Heat pumps are more efficient as long as it isn't too cold outside. As it get's colder and colder the heat pumps become less efficient. In, NC the temperatures usually stay warm enough for heat pumps to work well.