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Discussion Starter · #1 ·
I am getting ready to build my first house around dallas, tx and am wondering a few things about the codes. With more insualtion and tigher closed in homes, the 2012 irc calls for "a whole-house mechanical ventilation system for homes". What does this mean?

Isn't it conterproductive to close a house up so tight and then be forced to bring in fresh air mechanically only to have to heat or cool that air?
 

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diplomat
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You only have to heat or cool 20% of that air if you're using an HRV or ERV.

Even with just a fan, at least you will have control over how much fresh air you get.
 

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Discussion Starter · #4 ·
Fresh air intakes can be directly piped from the system to the outdoors.
You don't have to buy ERV?

What do you need to do... run a vent from the outside into the return with a 1 way valve on it?

What size pipe like a 1 1/2 or 2? It would need to be pretty small right?

I am looking to do a 1400 square foot house.
 

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You don't have to buy ERV?

What do you need to do... run a vent from the outside into the return with a 1 way valve on it?

What size pipe like a 1 1/2 or 2? It would need to be pretty small right?

I am looking to do a 1400 square foot house.
Cant say for certain I dont HVAC. The make up air needs to be calculated. I thought it would be a 4" round duct with a damper. On the return. Something to that effect.
 

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Discussion Starter · #6 ·
I was just wondering the cheapest and simplest way to still meet the code. Its hard enough for a homeowner to keep up with their return filter on their a/c without another piece of equipment to have to maintain.
 

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I think it runs on the same filter, maybe a simple mechanical damper when it powers up. I know my guy has used them when there is inadequate return air which can freeze up the evaporater.
 

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Discussion Starter · #8 ·
I think it runs on the same filter, maybe a simple mechanical damper when it powers up. I know my guy has used them when there is inadequate return air which can freeze up the evaporater.
I was looking at a broan and they have a filter that has to be washed every 3 months I think. The one I was looking at runs on a timer 20 on 40 off is normal opperation.

If you do a return/return install, it seems kinda nuts that the thing would run on a timer instead of when the a/c turns on. If the a/c was off and the erv was running, it would just be recycling its own air. I will find the install guide I was looking at.
 

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Use an ERV or HRV. Then use a good thermostat that can control it and your central HVAC system. So that the system blower comes on anytime the HRV/ERV is running.

You can also tie your bathroom exhaust into it, and have fresh air come in when the bathroom exhaust are used.
 

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Sean
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A few quick thoughts - be careful running an ERV 24x7, as you will have issues with humidity & in fact I would consider going with an HRV just do to that

As for venting a bath through an ERV there is a simple term for that & that is stupid especially in your climate - using an HRV is a hair above that do to the way it works.

For other options - pros & cons: http://blog.sls-construction.com/2013/bs4d-ventilation-strategies
 

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An HRV will bring in the high humidity air in the summer, and lower your humidity in the winter. Which isn't what you want.

An ERV will reduce the amount of humidity brought into or removed from the home.

Using the ERV for exhausting the bathroom prevents the extreme humidity changes that you can get by just bringing fresh air straight in.
 

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Sean
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An HRV will bring in the high humidity air in the summer, and lower your humidity in the winter. Which isn't what you want.

An ERV will reduce the amount of humidity brought into or removed from the home.

Using the ERV for exhausting the bathroom prevents the extreme humidity changes that you can get by just bringing fresh air straight in.
Correct on the moisture transport of an HRV as there is no filter to act as a block. Unfortunately an ERV has that block which essentially allows all the humidity in and doesn't allow hardly any out so the levels keep building up & up. Been there, done that, got the sweat stained t-shirt from using them down there. Shoot in many cases, many are looking at using in-line dehumidifiers do to this issue

As for the bath - sorry but no, it needs its own dedicated exhaust source just like a kitchen does no matter the climate.
 

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Discussion Starter · #15 ·
Correct on the moisture transport of an HRV as there is no filter to act as a block. Unfortunately an ERV has that block which essentially allows all the humidity in and doesn't allow hardly any out so the levels keep building up & up. Been there, done that, got the sweat stained t-shirt from using them down there. Shoot in many cases, many are looking at using in-line dehumidifiers do to this issue

As for the bath - sorry but no, it needs its own dedicated exhaust source just like a kitchen does no matter the climate.
Is an HRV is maintainance free?

Are there maintaince free erv?

I just want to put the thing in the crawlspace and forget it.
 

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I think the discussion gets modified a little bit from the humidity / AC end. If you put an AC unit in that also will dehumidify, that's really the one you want. Otherwise, you're going to have some very muggy indoor air, which is pretty uncomfortable in that location.

I've seen the HVAC mounted in the attic, and I've seen it sitting in conditioned space. For a house that size, it's probably going to be located in the attic, so you'll have a lot of attic runs. You need to think about what's going to happen when a run starts leaking.

Heat and hot water are usually gas in that area, so performance of an envelope / ventilation is a little different.
 

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Sean
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You guys know that the code requirement does not require you to put in a HRV or ERV system right?

One of your bathroom exhaust fans could cover the requirement, depending on how big the house is, etc.

Andy.
Yes indeed but... exhaust only is not a good practice where AC is used and especially not in humid areas as you are pulling moisture into the structure where you know it will find a nice condensing surface.

He could go with a pressurize only type of system but those also have there drawbacks
 
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