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Mailman

Exhaust venting feedback requested

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Mailman

Hiya all. I am by no means an expert on anything and usually stumble my way through just about everything I do. I am hoping some of you experts can give me some feedback on this project.

 

We plan on extending the back of our house all the way to the property line. As it is to be a firewall, all of the rooms sharing that rear wall (2 bedrooms/2 bathrooms) will no longer have windows.

 

To prevent the air in these rooms (especially the bathrooms!) from stagnating with hot, humid air, I am thinking of running some duct work between the roof and the ceiling panels along the back wall to which all of the affected rooms will be connected by way of ceiling-mounted exhaust fans. The ducting will either run up and through the roof ending in a turbine ventilator or straight out the side of the house with a larger fan to help draw the air out. Perhaps this fan will be solar-powered since it will run practically all of the time. All of the ceiling-mounted exhaust fans will be individually switched on and off as necessary.

 

We don't have air conditioners nor do we plan on getting any. Our screened windows and doors are usually wide open with the exception of the doors closing at sleepy time and everything being secured when no one is home.

 

Of what sort of locally available materials can the ductwork consist? I know a place that will fabricate sheet aluminum in whatever configuration I could possible come up with but I am wondering if a larger diameter (4" or 6") PVC tubing (the orange stuff) would work as the main duct? Seems like it would be easier to rig together. Or is that just plain silly?

 

How large does the main duct actually have to be to efficiently move air? The entire house (pre-extension) is only 80sq m so all the rooms are pretty small.

 

Do the bathrooms need to have their own seperate ducting or is it okay to share the other rooms' ducting?

 

I would appreciate any recommendations, pointers, or even snide comments completely unrelated to the topic at hand! :thats-funny:

 

Thank you for your time.

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Mailman

No experts in this area, eh?

 

No worries. :biggrin_01:

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sjp

No experts in this area, eh?

 

No worries. :wink:

 

Well do get any air flow in my house in Canada, I have a furnace blower which is pretty big and duct work that is 8" by 12" for the main and each room is 4" diameter. So you do get a good draft you would need a big fan or blower

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Ozepete

No experts in this area, eh?

 

No worries. biggrin.gif

 

Hi Mailman:

I would suggest using a ceiling mounted exhaust fan for each room specially the bathroom. (variable speed ones for the bedrooms) . Also cut 20mm off the bottom of each door of these rooms.

This would cause air to exhaust into the ceiling / roof cavity.

Then consider vent slats under the eaves of a wall in each direction. (one set under the eave on the north side and so on) This would cause air to enter naturally and travel though the roof cavity. This air movement / replacement would keep the air fresh and remove heat at the same time. I hope this helps..

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Mailman

Hi. Thanks for the responses.

 

I guess what I am really looking for is if my plan is not only do-albe, but also reliable/efficient/correct.

 

Incoming air drawing from the rest of the house isnt' really a problem. The doors of all the rooms have a good clearance from the floor, but the doors themselves are opens probably 99% of them time anyway. The bathroom doors are those cheap PVC 'Pretty Doors' that have the slated vents near the bottom as well.

 

The eaves of the house already have vents (soffit?) but I don't really see any vents at the ridge of the roof (probably hidden within). I am sure air finds a way out though. Anywhooo... this part is moot since I don't plan on venting the rooms directly into the ceiling space.

 

I would like to run some ductwork along the ceiling space over all the affected rooms and eventually terminating at the side of the house (with fan) or throught the roof (turbine ventilator). Which one is best? I hear that turbine ventilators have a tendency to fly away in high winds, but can that be rectified with additional reinforcement?

 

Also, should I stick with aluminum sheeting for the ductwork itself or is large diameter PVC a viable alternative?

 

Is this really as easy as it sounds?

Edited by Mailman

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Headshot

Hi. Thanks for the responses.

 

I guess what I am really looking for is if my plan is not only do-albe, but also reliable/efficient/correct.

 

Incoming air drawing from the rest of the house isnt' really a problem. The doors of all the rooms have a good clearance from the floor, but the doors themselves are opens probably 99% of them time anyway. The bathroom doors are those cheap PVC 'Pretty Doors' that have the slated vents near the bottom as well.

 

The eaves of the house already have vents (soffit?) but I don't really see any vents at the ridge of the roof (probably hidden within). I am sure air finds a way out though. Anywhooo... this part is moot since I don't plan on venting the rooms directly into the ceiling space.

 

I would like to run some ductwork along the ceiling space over all the affected rooms and eventually terminating at the side of the house (with fan) or throught the roof (turbine ventilator). Which one is best? I hear that turbine ventilators have a tendency to fly away in high winds, but can that be rectified with additional reinforcement?

 

Also, should I stick with aluminum sheeting for the ductwork itself or is large diameter PVC a viable alternative?

 

Is this really as easy as it sounds?

I hit the wrong button (thank), but you don't get thanked enough anyway, so I guess it's OK.

 

If your attic area is open, why use ducting at all? Just exhaust your ceiling exhaust fans directly into the attic area and use a big gable-mounted exhaust fan to pull the warm air out. You can get a thermostat-controlled fan for the gable that will keep your whole house cooler all the time in addition to pulling out the air coming through the exhaust fans. Just be sure to put some screen over the top of the ceiling-mount exhaust fans to keep the critters from using it as a door into your home.

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USMC-Retired

Your bathroom should have a vent. You can buy them to run on a timer or by switch. The additional humidity and the water retention of concrete will cause a serious mold problem. Just vent it to the attic or out side.

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Mailman

I hit the wrong button (thank), but you don't get thanked enough anyway, so I guess it's OK.

 

If your attic area is open, why use ducting at all? Just exhaust your ceiling exhaust fans directly into the attic area and use a big gable-mounted exhaust fan to pull the warm air out. You can get a thermostat-controlled fan for the gable that will keep your whole house cooler all the time in addition to pulling out the air coming through the exhaust fans. Just be sure to put some screen over the top of the ceiling-mount exhaust fans to keep the critters from using it as a door into your home.

 

Well, I suppose that would work but I heard that bathrooms should really be vented directly outside for the exact reason Norseman stated (below).

 

I was planning on screening off the exit end to keep them out of the ducting itself. I'd have them big geckos (tuko) in there for sure. :wink:

 

Your bathroom should have a vent. You can buy them to run on a timer or by switch. The additional humidity and the water retention of concrete will cause a serious mold problem. Just vent it to the attic or out side.

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Headshot

Well, I suppose that would work but I heard that bathrooms should really be vented directly outside for the exact reason Norseman stated (below).

Your bathroom should have a vent. You can buy them to run on a timer or by switch. The additional humidity and the water retention of concrete will cause a serious mold problem. Just vent it to the attic or out side.

Exactly. If the attic will be vented, then you won't have mold problems there either.

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USMC-Retired

What you do not see here is those silver whirlly things on peoples roofs. If you had a few of those the temp in the attic would reduce significantly thus in your house also. Additionally if you put vents in the rooms to the attic with of course screen to prevent the little critters then you will not see a mold or mildew problem in the rooms. Also the temp will be reduced. In real hot climates there are even big exhaust fans in the attic that sux the air out (as stated above). It will then pull the air through out the house.

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Mailman

What you do not see here is those silver whirlly things on peoples roofs.

 

A turbine ventilator. I mentioned that as a possible duct termination.

 

I am hestiant about that particular option due to the strong winds during typhoon season. Don't want it to fly away. :wink:

 

I could, however, mount it near the firewall and add extra braces for support.

 

The other option would be to end the duct work straight out the side of the house with a larger fan to assist drawing the air out.

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Headshot

What you do not see here is those silver whirlly things on peoples roofs.

 

A turbine ventilator. I mentioned that as a possible duct termination.

 

I am hestiant about that particular option due to the strong winds during typhoon season. Don't want it to fly away. :wink:

 

I could, however, mount it near the firewall and add extra braces for support.

 

The other option would be to end the duct work straight out the side of the house with a larger fan to assist drawing the air out.

The less ducting you use, the better off you will be. Your room fans will run more efficiently without the ducting. Just use a gable fan (thermostat-controlled or switched) and your attic will be vented without having to worry about typhoons (the louvres are closed when the gable fan isn't operating, so you don't need to worry about water coming in). Any moisture from the room fans will be vented out and your house will be cooler throughout.

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m60man

Ok, mailman, hope this helps. First each bathroom (CR) should be vented separately. 4" PVC will be fine to use. I recommend venting them outside in be sure moisture is exiting the house. A common exhaust or exhaust/light combination will work fine. If possible try to vent them through the wall under the soffit. No need to put holes through roof and end up with possible leak. The other two rooms, I would do the same except they can be vented together above the ceiling and then exit the house. Use Y's and 45's fittings if needed. Avoid regular Tee's and 90 degree elbows. Cover exit points with decorative trim, screen or vent covers. Most stove vent-a-hoods are vented using 3" or 4" PVC. here and work fine. Long runs might dictate larger ducts, but in your case 4" will do the job. Hope this is helpful.

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booger10

What you do not see here is those silver whirlly things on peoples roofs.

 

A turbine ventilator. I mentioned that as a possible duct termination.

 

I am hestiant about that particular option due to the strong winds during typhoon season. Don't want it to fly away. :P

 

I could, however, mount it near the firewall and add extra braces for support.

 

The other option would be to end the duct work straight out the side of the house with a larger fan to assist drawing the air out.

 

There should be attic fans that you should be able to get there. It blows air out the gable of the attic rather than the roof. And, you might be able to get one temperature contolled. If it gets to a certain temperature in the attic, it will start, when enough cooler air goes into the attic it will stop. It does not take much energy and will actually help keep the house cooler. Insulation across your ceiling should keep the heat from the rooms, too. If you use regular vents from each room, you can balance the airflow by how much you close the vent===less airflow from smaller rooms, etc. This would be the opposite of a regular air conditioning system which would have a return air duct. (smile) instead of an airflow meter which you would use in the attic, you could use one of those little toys like fans that twirl... get it to turn about the same with each vent..then you will have equal volume of air from each room..if you have too much air from one room, very little will go from smaller rooms and defeat the purpose of taking out heat and moisture.

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