Fresh Air Intake (for house)

[awdblazer]

so i have been noticing more and more condensation on my windows in my house
the furnace is a high efficient with its own intake and exhaust
my house doesnt have any fresh air intakes
it has two exhaust fans one in each bathroom
my question to everyone as a hrv is too expensive and wouldnt work correctly in my house
do i just run a 6 inch damper from outside to the cold air return ducting
then can i use a 24v contactor with 120v contacts to fire my exhaust fans on when its calling for fresh air?
thanks

 

[yeldogt]

There are many reasons for high humidity -- and HRV's are not often the best way to address. You may need a dehumidifier ... uncontrolled fresh air only works when outside is lower and it can be very inefficient.


you send to discover the RH .. where is coming from. sometimes leaking windows can sweat .. and humidity is not all that high

 

[awdblazer]

windows are brand new and i am slowly upgrading doors and insulation

 

[eddieK]

This is mostly a result of houses today sealed up very tight.

You can simply add one small (6" or 7" duct)filtered (or be sure it attaches to the return upstream of filter) outside fresh air to the system with an air volume control damper...this way that outside air is heated without using strip heat (HRV)...Electric strip heat kinda defeats energy savings...

 

[ItsNemo]

Why wouldn't an HRV work? They aren't that expensive.

Alternatively, how about just running a regular plug in dehumidifier? Along with circulating the air in the house it should help to dry things out.

 

[awdblazer]

with an hrv they are fairly big and my utility room isnt very big and you need minimum 6 feet away from other vents so the hrv has a intake and exhaust so thats two 6 inch holes
and a hrv is about 1500 just for the hrv not including installation
whereas a damper is about 200 bucks and the contactors are fairly cheap

 

[LS6 Tommy]

Unfortunately, If your windows are sweating, they aren't very efficient, regardless of whether you have a source of fresh air or not.

Tommy

 

[JRC3]

The problem I see with pulling cold air from the outside into a furnace return is condensation. Either in the duct or in the heat exchanger. IDK, I'm no HVAC guy

I've looked and I've seen HRVs for around $700 and even small ceiling mounted 40-50 cfm for around $250 or so. Not sure of the efficiency ratings. Your outside temps may require more than what I've looked at.


OP, do you have a crawlspace, basement, or attic? These are great places for an HRV, though you might be limited with snow depth in the crawl or basement, though there are plenty of ways around that.

One question: Do you have a humidifier running? And maybe one more question: Are you bathroom fans fully ducted to the outside?

There are many reasons for high humidity -- and HRV's are not often the best way to address. You may need a dehumidifier ... uncontrolled fresh air only works when outside is lower and it can be very inefficient.

That's an idea. A simple dehumidifer might really help. I have one in the crawlspace. It works down to like 40F, not that the OP needs that, but it also has a condensate pump to empty the tank. I don't use that, but it's there. I got it on sale for like $300 out the door with extended warranty.

This is it and it has all the functions you need to be hassle free. I'm sure it's available in Canuckland. https://www.menards.com/main/heatin...e-95ip-01/p-1479280788202-c-1497103338432.htm

 

[awdblazer]

basement
attic but its unconditioned and my furnace is in the basement
running my dehumidifier does not much
windows are the most efficient windows you can get

 

[LS6 Tommy]

Which windows do you have? If you're getting sweat on the room side of the windows, then they aren't insulating properly or there's a draft across them. If it's in between the panes, the seal is bad.

Tommy

 

[walta]

The condensation may be normal. If it is -10°F outside and it is 75° 65% humidity inside with single pain windows.

First what is
1 the outdoor temp?
2 the indoor temp?
3 the indoor humidity?
4 window type double pane? Uvalue?
5 Has the home been tested with a blower door?
6 Do you have bath fan that you use?
7 Do you have a range hood that you use?
8 Do you have an indoor swimming pool, aquariums, hot tub or lots of indoor plants?
9 Any unvented heaters?

The only way to get rid of the condensation is to install better windows or lower the indoor humidity. It is best to control the moisture at the source if that is not possible then vent it is the source.

I do not think you want to vent your house unless it had been proven to be very tight with a blower door test only then you would need a heat recovery ventilator HRV.

Walt

 

[yeldogt]

HRV's will reduce inside humidity only if the outdoor humidity is lower -- and you have to be careful when snow is on the ground w/sunlight as the humidity may be high at ground level where many of the intakes are.

That's not the primary reason to have one -- using in this way causes the unit to run much longer than needed many times of the year. The primary reason is to bring in fresh air -- replacement air for a tight houses that does not breath.

You are better off using a dehumidifier w/ controller -- this will bring in air through a humidifier loop.

make sure you have good exhaust fans

 

[LS6 Tommy]

The condensation may be normal. If it is -10°F outside and it is 75° 65% humidity inside with single pain windows.

Walt

True.
When he said he had "the most efficient windows" I just made the assumption they were at least dual pane...

Tommy

 

[Dkramer]

I live in Oregon, an with the energy code the way it is, houses are build so tight the air inside can get stale and they can sweat. One of the ways around this is to provide outside air. We do that by installing a duct in the return air that is bringing in fresh outside air. It has a power driven damper with a control that is set up for the size of the house how many occupants, and how much fresh air you want. When the fan comes on, the damper opens. If the fan hasn't run for sometime, the control will open the damper and turn on the fan to meet the requirements it is set for. The only problem is around here we can have several smoke filled weeks because of near by forest fires. These will bring that smoke filled air into the house. You wouldn't believe how many calls we got the first year we started putting these on and had a bad fire year. They do have a switch to disable them, however. Makes sense doesn't it. We have to build houses now that are so tight we have provide fresh air.

 

[awdblazer]

windows i have are triple paned
dkramer thanks!!! what about exhaust?

 

[Tracs]

windows i have are triple paned
dkramer thanks!!! what about exhaust?

Your situation has me baffled. I install ductwork, furnaces, and HRVs in Brandon, MB. My house is old but with new windows, doors, furnace and is dry as a desert. My brother's house in 3 years old and water pours off the windows. We had to pretty much close the fresh air intake damper on the HRV to reduce the humidity in his house.

So we have one old house without a HRV that could start on fire in a rainstorm, and a brand new house that will melt into a soggy pile of mush. We are in the exact same climate and region as you.

There is a reason other than no HRV as to why your house is so humid. Sorry I don't know why though.

 

[Dagny]

Check the installation manual that came with your furnace and see if it can run with one pipe. This will not work if your furnace is in a small room or closet but if it sits in the middle of a large basement and is allowed by the furnace mfg. This will give you some more exhaust at no cost.

 

[yeldogt]

Your situation has me baffled. I install ductwork, furnaces, and HRVs in Brandon, MB. My house is old but with new windows, doors, furnace and is dry as a desert. My brother's house in 3 years old and water pours off the windows. We had to pretty much close the fresh air intake damper on the HRV to reduce the humidity in his house.

So we have one old house without a HRV that could start on fire in a rainstorm, and a brand new house that will melt into a soggy pile of mush. We are in the exact same climate and region as you.

There is a reason other than no HRV as to why your house is so humid. Sorry I don't know why though.

HRV can only reduce humidity when the humidity is low outside -- and then it's not stripping the humidity out of the air... it's only reducing it under ideal conditions. Other times it's actually raising it. Most tight houses have to have good exhaust vents for the kitchen and bathrooms -- get the humidity out quickly. It's a small penalty. Really tight houses sometimes need dehumidifiers -- incorporating them at the beginning is the way to go ... I skip the HRV/ERV

 

[JRC3]

Most tight houses have to have good exhaust vents for the kitchen and bathrooms -- get the humidity out quickly.

That's a good thing to think of. Many hoods and microwave combos are not directly vented to the outside and only blow the air away from the cooking surface into the room.

IMO bathroom fans should be wired with a shower light so they actually get used. And of course, directly vented to the outside.

 

[yeldogt]

That's a good thing to think of. Many hoods and microwave combos are not directly vented to the outside and only blow the air away from the cooking surface into the room.

IMO bathroom fans should be wired with a shower light so they actually get used. And of course, directly vented to the outside.

I use the Fantech units w/ electronic timer switch -- particularly like the exterior unit -- if it can be hidden. They allow for two vents inside the bath (shower and toilet)

I have heard all the cases made of using HRV/ERV for general ventilation -- placing them into bathrooms .. some have boosters. I don't think they work as well as just doing dedicated systems -- and it's cheaper.

 

[Dkramer]

windows i have are triple paned
dkramer thanks!!! what about exhaust?

Your range vent and bath vents are all you need. You will be slightly pressuring the house so it will find its way out thru them, even if they aren't on. Of course having then on will hasn't the removal of high humidity, as was stated earlier. One of the features the electricians install in some of the houses is bath fan timers that will cycle the fan every so often.

 

[awdblazer]

Your range vent and bath vents are all you need. You will be slightly pressuring the house so it will find its way out thru them, even if they aren't on. Of course having then on will hasn't the removal of high humidity, as was stated earlier. One of the features the electricians install in some of the houses is bath fan timers that will cycle the fan every so often.

would me getting a relay to pickup when the furnace kicks on to turn the exhaust fans a good idea or bad idea?

 

[yeldogt]

You don't want to have a negative pressure system for fresh air. The range and bath fans are to get the most troublesome air out of the house pronto .. most house leak enough where this is not a problem .. but some don't and you need makeup air.

In some climates the simple intake to the furnace will work .. but in any areas with humidity this will not work -- yes it will replace the stale air ... but it will not fix the humidity problem .. even make it worse.

There are many controls available to operate dampers -- and even the furnace to circulate the outside air .... but ...again .. this will not fix your problem.

Many times kitchen and bath exhaust fans are too small .. and are not removing the moisture from those sources.

A tight house with many people may need a dehumidifier -- you can get one that will have it's own controller -- it can bring in outside air and condition it and the inside air as well. TEh better units work very well and are efficient.

 

[awdblazer]

what do u mean by native pressure system?
each of my bathroom fans are 100cfm and are ducted with 4 inch duct

 

[JRC3]

what do u mean by native pressure system?
each of my bathroom fans are 100cfm and are ducted with 4 inch duct

I figured "negative".

 

[yeldogt]

what do u mean by native pressure system?
each of my bathroom fans are 100cfm and are ducted with 4 inch duct

Sorry -- typing on an tablet ... Negative.


Have you checked that they are working correctly ?? vented properly outside away form any other vents?

 

[awdblazer]

yup but basement one hardly ever runs as we dont use that bathroom shower
the upstairs one runs whenever we need it

 

[yeldogt]

if exhaust vents are working it's people or moisture coming into the house some way ... a very tight house will need a dehumidifier if enough people per square foot ...peopel toss off a lot of moisture.

 

[Blk88GT]

Have you checked the actual humidity level in the home? What temperature do you keep it inside?

 

[awdblazer]

so i took your guys advice and put the dehumidifier on and kept the furnace fan on and no condensation
thanks!!!

 

[Falcon67]

You don't want to have a negative pressure system for fresh air. The range and bath fans are to get the most troublesome air out of the house pronto .. most house leak enough where this is not a problem .. but some don't and you need makeup air.

This. We still have leaks but we really worked at sealing things up. With two bath fans and the big kitchen vent running, it's like a mini blower door test on the house. It'll pull an outside door open quick. And that's with a fire place that uses only a light weight steel damper. A tight house doesn't get the same use out of a bath vent that a loose one does - has to pull air from somewhere. We are so dry here typically that we don't even turn the fart fans on, we need the moisture in the house LOL.

 

[DC73]

so i took your guys advice and put the dehumidifier on and kept the furnace fan on and no condensation
thanks!!!

I'm late to the thread but if you think you might still need to ventilate better, here are a couple of good articles on the subject:

http://www.greenbuildingadvisor.com/blogs/dept/musings/designing-good-ventilation-system

http://www.greenbuildingadvisor.com/blogs/dept/musings/hrv-or-erv

DC

 

[Trey T]

Fresh air intake isn't going to work to control humidity. The best way to control humidity is to keep the house tight and use your HVAC system to control it; how you control it can be a challenge.

My house have condensation at windows (not all windows) and it's simply because the return grille is on the other side of the house. Ideally, in order to precisely control your humidity, you need appropriate numbers of return air grille in every room of your house.

 

[DC73]

The best way to control humidity is to keep the house tight and use your HVAC system to control it;

It's also best to make sure the HVAC is sized correctly. Too large of an AC unit will short cycle which means it won't run long enough to extract sufficient humidity. Also, an ERV is tailor made for those of you in very humid climates who also need to bring in fresh air for ventilation.

DC

 

[TomC750]

We have a sandwich panel house with hot water baseboard heat and an air to air heat exchanger. We found it is more effective to run it for 2 hours in the afternoon than for the same time at night. If it is not run, we do have condensation on our low E double pane windows. We only run it in the winter. House is in upstate NY.

 

[Copymutt]

My money's on your bath fans, dryer not being used or not properly venting.
Jim

 

[yeldogt]

In the summer with a properly sized AC system and hot outdoor temps -- the system will run enough to control the humidity. Likewise in the winter months when the outside air is very dry .. most houses don't have a problem unless small w/many people. But, if they do have a problem in the winter there is no solution other than some form of dehumidifier. There are many days when the outside air is too humid to reduce inside air with only the mix of an HRV/ERV

I like dedicated bath exhaust fans .. because they work ..and work quickly. They do create some negative pressure and this needs to be assured within acceptable limits ..but they don't have to run very long and the loss is minimal. HRV/ERV's are often on many hours and can be real energy wasters.

Having an outside intake running through a dedicated dehumidifier with controller works for me ... it's simple and does two things at once. Ventilate a tight house and dehumidify if required. These can be tied into the HVAC ductwork or use dedicated returns. The controller manages the damper and the dehumidifier ... it's also easy to include a makeup damper and control for the range hood within the same system.

 

[slimcake]

Outside Air Temperature (oF) Inside relative humidity for 70 indoor air temperature
-20 -29 15% or less
-10 -23 15% to 20% humidity
0 -18 20% to 25% humidity
+10 -12 25% to 30% humidity
+20 -7 30% to 35% humidity

You won't find a house much more efficient than what I just built. This is what I go by. It ***** cause its close to ****** nose range but its what it takes. PS my house is in MN and my gas bill hasn't been over 150 a month and elec. is running right about 100. Actually 70 when you take the 30 dollar meter charge off.... I use a air to air exchanger which I believe is code in MN now.