Fresh air vs losing heat

[mikebsnyder]

I may have made my new shop too tight. It’s 48x80x16 finished inside with metal. I urethaned the walls then batted, and the attic has 18inches of blown. I still haven’t figured out heat. Was thinking of just some blue flame vent free wall hanging units but I’m a little concerned about fresh air. It’s a large volume area but if say I don’t really open it until spring there’s not a lot of opertunity for fresh air. Also if I start up my tractor to go plow yeah I’ll open an overhead but I’m thinking unless it’s windy or I open a second door the fumes probably won’t have a chance to fully vacate. Do I need an exhaust unit? Would I need two - one to pull air in the other to move it out?

 

[The Cobbler]

get vented units

 

[e-tek]

Most ceiling mount units vent to the outside so they just recirculate the air, heating it as it goes through. A CO detector is useful tho.

 

[Stuart in MN]

Yes, use vented heaters. There's no good reason to use ventless.

 

[mikebsnyder]

Where do they draw fresh air from? Just the room volume?

 

[NUTTSGT]

Where do they draw fresh air from? Just the room volume?

Depending on the type of heater, some have ducting to draw outside air. Much like a exhaust vent but for fresh combustion air.

 

[58Yeoman]

Don't go ventless. My shop is 24x40 with a Big Maxx heater (75,000 btu). It's nice to never have to worry about fumes or if I have enough fresh air. It vents to the outside and draws combustion air from the shop.

Off topic, but some corn/pellet stoves have a 'double wall' pipe that draws combustion air through the outside pipe and exhausts through the inside pipe.

 

[CraigStu]

I like ventless. We heated our little 1500 sq ft house w/ one for 20 yrs. Our current house has a natural gas fireplace which we really like. But so much heat goes outside it is ridiculous. We are now building our retirement home and I have done a bunch of internet searching for a propane heating stove. What I have found is that the best efficiency rating for a vented unit is about 80%. The efficiency for most any ventless unit is 98-99%.

 

[ishiboo]

Ventless puts 100% of the combustion moisture into your air. They're quite safe but that's a lot of moisture to deal with.

I like ventless. We heated our little 1500 sq ft house w/ one for 20 yrs. Our current house has a natural gas fireplace which we really like. But so much heat goes outside it is ridiculous. We are now building our retirement home and I have done a bunch of internet searching for a propane heating stove. What I have found is that the best efficiency rating for a vented unit is about 80%. The efficiency for most any ventless unit is 98-99%.

I am putting a normal home furnace in mine. 98% efficient, no combustion gasses in the room and doesn't add any moisture.

 

[buzzworth]

There's the option of using an ERV unit. When we built our home we incorporated one in the HVAC system. The house was built with SIPS and spray foam insulation and is so tight we have to open a window when we turn on the fan over the stove.
This would circulate outside air into the building without losing the temperature.

https://www.renewaire.com/our-ervs/single-multi-family/ev-single-multi-family/

 

[kbs2244]

Go with vented IR units.
Great heat with minimum warm air loss.

 

[Jackfre]

You will be best served with a direct vent heater. That way, you get the comfort of your heater without sacrificing the investment in Insulation.

 

[yeldogt]

The blue flame wall units are no different vs turning on your oven and sticking your head inside. They are allowed because they have a relatively low BTU output and state very clearly in the sales and install manuals that they are only to be used for supplemental heat.

Same with the fireplace inserts -- it's amazing to me they are allowed. They have to be almost 100% efficient -- everything is going into the space! Propane units are especially nasty -- propane is a by product and can be made of of all kinds of nasty stuff .. it's dirty when compared to NG.

Most garage heaters are 80% and use room air for combustion -- expelling though a typical metal flue. I have a cabinet unit that is a sealed combustion unit -- it uses outside air to feed the flame through a tube. It's still only 80 %

 

[HoosierBuddy]

I like ventless. We heated our little 1500 sq ft house w/ one for 20 yrs. Our current house has a natural gas fireplace which we really like. But so much heat goes outside it is ridiculous. We are now building our retirement home and I have done a bunch of internet searching for a propane heating stove. What I have found is that the best efficiency rating for a vented unit is about 80%. The efficiency for most any ventless unit is 98-99%.

I completely disagree with this assessment.

Ventless heaters are neither recommended, suitable, or appropriate for use as a primary form of heat in a home. All of them are limited in BTU capacity due to the concern that they will adversely affect the amount of oxygen in the heated space (hence why they all have O2 depletion sensors incorporated in them) if they are burned for too many hours, in too tight of a space, or in too small of a room. Many (perhaps MOST) of these units include warnings to crack a window whenever they are in use just because of this.

I'm not completely against them by any means. I have 2 installed in my home, one as a fireplace log set that gets turned on once or twice a season and one as a freestanding spaceheater that runs perhaps an hour a day through the winter. They are fine for that type of use but SHOULD NEVER be used in place of a furnace or other full time space heating option.

They are particularly poorly suited for a garage where solvents, dust, etc, can be pulled into the burner and returned to the heated space causing noxious odors and fumes that can lead to watering eyes, headaches, etc.

Just my informed opinion after 25 years of experience.

Phil

 

[danski0224]

I may have made my new shop too tight.

If you can breathe in the shop with the doors and windows closed, it isn't too tight

As far as makeup or combustion air is concerned, follow local codes and installation instructions.

 

[Showkey]

Yes ...safety is for sissies

If your nose still works............it tells you ventless is a really really bad idea. Then half the stuff that’s bad is odorless.

This is spot on:
“They are particularly poorly suited for a garage where solvents, dust, etc, can be pulled into the burner and returned to the heated space causing noxious odors and fumes that can lead to watering eyes, headaches, etc.”

https://emergency.cdc.gov/agent/phosgene/basics/facts.asp

Brake clean fumes passing through a flame......

Google phosgene gas:
Phosgene can be formed when chlorinated hydrocarbon compounds are exposed to high temperatures. Chlorinated hydrocarbon compounds are substances sometimes used or created in industry that contain the elements chlorine, hydrogen, and carbon.
The vapors of chlorinated solvents exposed to high temperatures have been known to produce phosgene. Chlorinated solvents are chlorine-containing chemicals that are typically used in industrial processes to dissolve or clean other materials, such as in paint stripping, metal cleaning, and dry cleaning.
Phosgene gas is heavier than air, so it would be more likely found in low-lying areas.