EcoRenovator  

Go Back   EcoRenovator > Improvements > Conservation
Advanced Search
 


Blog 60+ Home Energy Saving Tips Recent Posts Search Today's Posts Mark Forums Read


Reply
 
Thread Tools Display Modes
Old 04-16-12, 07:36 PM   #1
Drake
DIY Guy
 
Join Date: Jan 2011
Location: Mpls,MN
Posts: 315
Thanks: 2
Thanked 17 Times in 17 Posts
Default Indoor air quality discussion

Indoor air quality is the last major area of concern in the design and construction low energy demand retirement addition to our existing weekend home. It is a major one that is only an issue for our heating season when closing the designed air tight enveloped living space is not well ventilated by air infiltration or open windows/doors. I know air/air HX's are proposed to be the solution but I am not sold on that for a modest low heat demand space. Their high commercial cost and installation, working life span and design problems in very cold climates(frosting) makes them questionable of being cost effective. Methods to eliminate frosting add to the cost. Energy saving and efficiency percentages are relative. A 50% are something of a $1,000. heat bill but not a $30. one if it cost $1,000.'s to do so.

When a heated space becomes insulated/air tight enough heating required air exchange becomes the sigficant factor so minimizing it need is an important goal. DIY air/air HX should make it less costly and that is being discussed in another thread. I would like to disscuss/explore other possible means or reduction of the needed exchange amounts for a heathy living space that might eliminate HX's or at less make a less efficient easier/cheaper DIY recovery HX buildable.

Some points of discussion: -eliminating/minimizing pollution sources VOC's, radon, etc. -solar daytime fresh air heating thru collectors. -storage of daytime solar energy to warm fresh air at night. -amount of fresh air needed thru night time vs day time. I am interested in anything on this topic. I just believe there is an more practical path to go for low energy demand space.

For my project of 8,000. cubic feet of space the ASHRAE recommended minimum exchange rate of .35 ACH would require heating 67,000 cu' of air every 24hrs. I need to calculate how many BTU's that needs especially as my heat source is radiant which doesn't need to heat the air as much to feel the same temp. to get an idea what is a reasonable amount to pay to offset just taking in fresh air.

I've always lived with the maxim "The best way to save a dollar is
not to need to spend it".

Drake is offline   Reply With Quote
Old 04-17-12, 07:18 AM   #2
S-F
You Ain't Me
 
S-F's Avatar
 
Join Date: Nov 2009
Location: Northampton MA
Posts: 662
Thanks: 6
Thanked 70 Times in 58 Posts
Default

If you have direct vent heat/hot water you can install a good range hood and just rely on negative pressure to bring fresh air into the house. Some people are installing a bath fan on each floor on a 24 hour timer and putting Aldes Airlet vents in the bedrooms and living rooms

Airlet 1000 - Make-Up Air Solutions - American Aldes Ventilation Corporation
__________________
My project:


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


Chipping away on a daily basis.

Quote:
You know you're an ecorenovator if anything worth insulating is worth superinsulating.
Quote:
S-F: "What happens when you slam the door on a really tight house? Do the basement windows blow out?"

Green Building Guru: "You can't slam the door on a really tight house. You have to work to pull it shut."
S-F is offline   Reply With Quote
Old 04-21-12, 06:02 PM   #3
herlichka
Apprentice EcoRenovator
 
Join Date: Oct 2010
Location: Simcoe County, Ontario, Canada
Posts: 102
Thanks: 11
Thanked 15 Times in 10 Posts
Default

Your heating system is only partly responsible for air quality issues. Cooking, bathing, laundry, house plants, breathing and perspiration all contribute to indoor air quality, as well as chemical off-gassing from building materials, textiles and interior finishes. I think that a "heat recovery ventilator" is one of the best investments that you can make. They are simple and reliable, and your building Inspector may actually require that one be installed in your home.
herlichka is offline   Reply With Quote
Old 04-21-12, 08:38 PM   #4
RobertSmalls
Journeyman EcoRenovator
 
RobertSmalls's Avatar
 
Join Date: May 2009
Location: Buffalo, NY
Posts: 344
Thanks: 3
Thanked 17 Times in 15 Posts
Default

Air filtration can reduce (but certainly won't eliminate) the need for air exchange. My Honeywell air purifier seems to help a great deal with my allergies. If I were to keep replacing its charcoal filter, it would remove VOCs and other odors as well.

There are also ways to reduce the cost of HRV: http://ecorenovator.org/forum/conser...exchanger.html
RobertSmalls is offline   Reply With Quote
Old 04-22-12, 01:54 AM   #5
AC_Hacker
Supreme EcoRenovator
 
AC_Hacker's Avatar
 
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,002
Thanks: 303
Thanked 705 Times in 527 Posts
Default

You guys are forgetting minimum oxygen levels and at the same time, maximum CO2 levels... this is what brings on the 'stuffiness' sensation. In fact, I have seen technical specifications on commercial ventilating systems that have CO2 sensors that control the duty cycle of the air-exchange systems.

I don't think that there would be that much heat that would be lost in .35 ACH, (in your case 67,000 cu ft), especially when you consider that 5 to 7 ACH was considered acceptable a few years ago, which would be 7 to 20 times as much heat lost.

My house is approaching the stuffiness level. I had to work pretty hard to get there, too. I'm looking for, or will build a small .35 ACH high efficiency HRV, myself. I'm figuring that if I have a crowd of people in the house who are active or dancing, I can open windows to make up the difference.

-AC
__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker...
AC_Hacker is offline   Reply With Quote
Old 04-22-12, 11:48 AM   #6
MN Renovator
Less usage=Cheaper bills
 
MN Renovator's Avatar
 
Join Date: Nov 2010
Location: Minneapolis, MN
Posts: 930
Thanks: 41
Thanked 113 Times in 87 Posts
Default

"especially when you consider that 5 to 7 ACH was considered acceptable a few years ago"

5 to 7 being considered acceptable is ACH50. 5ACH at 50 pascals is what my house exchanged prior to any serious air sealing which happened to be mostly loads of leakage from the garage into the house through the sill boxes.

5ACH naturally infiltrated would chill a house in the winter really quick and if you changed the air out 5 times per hour your furnace would be a huge monster and I couldn't imagine the energy bills. You'd feel the air moving constantly and the comfort would be terrible because of it.

0.35ACH of ventilation either through forced ventilation or infiltration is quite a lot of air to move. In Minnesota the ACH50 to nat factor is 17. So if I take my previous 5ACH50 and divide by 17, I get about .3ACH natural. So basically a house built to have even a little thought to the basics of air sealing will probably need forced ventilation. If I had 4 adults in this house or a smelly baby, I might agree with ASHRAE or code requirements but I don't.
MN Renovator is offline   Reply With Quote
Old 04-22-12, 12:10 PM   #7
S-F
You Ain't Me
 
S-F's Avatar
 
Join Date: Nov 2009
Location: Northampton MA
Posts: 662
Thanks: 6
Thanked 70 Times in 58 Posts
Default

Yeah but you use a 60% efficient HRV and you get the benefits of fresh air (I don't think anyone here is going to argue about how important fresh air is) while being able to direct it exactly where you want it to go and remove the stale air from where IAQ is the worst. And to top it off you get a 60% return on your exhaust energy compared to leaks or negative pressure.

Seems like a no brainer to me, but there is the initial investment of $700 or so for the unit and ductwork if you don't already have that stuff.
__________________
My project:


To view links or images in signatures your post count must be 0 or greater. You currently have 0 posts.


Chipping away on a daily basis.

Quote:
You know you're an ecorenovator if anything worth insulating is worth superinsulating.
Quote:
S-F: "What happens when you slam the door on a really tight house? Do the basement windows blow out?"

Green Building Guru: "You can't slam the door on a really tight house. You have to work to pull it shut."
S-F is offline   Reply With Quote
Old 04-22-12, 01:03 PM   #8
MN Renovator
Less usage=Cheaper bills
 
MN Renovator's Avatar
 
Join Date: Nov 2010
Location: Minneapolis, MN
Posts: 930
Thanks: 41
Thanked 113 Times in 87 Posts
Default

The problem is if you have a retrofit to do and don't want to hire a contractor, you are pretty much out of the game to replace fresh air into the bedrooms and exhaust from the kitchen and bathrooms. That ductwork isn't very DIY friendly. The idea is great when you can have it implemented in new construction when its cheap to do and can be designed with a decently appropriate exchange rate. Of course new construction is primetime where you really need to replace the air from all of the contaminants leeching from the construction process and all the moisture involved in those components.
MN Renovator is offline   Reply With Quote
Old 04-22-12, 01:20 PM   #9
AC_Hacker
Supreme EcoRenovator
 
AC_Hacker's Avatar
 
Join Date: Mar 2009
Location: Portland, OR
Posts: 4,002
Thanks: 303
Thanked 705 Times in 527 Posts
Default

Quote:
Originally Posted by MN Renovator View Post
5ACH naturally infiltrated would chill a house in the winter really quick and if you changed the air out 5 times per hour your furnace would be a huge monster and I couldn't imagine the energy bills. You'd feel the air moving constantly and the comfort would be terrible because of it.
This is exactly the situation that many millions of homes experience right now.

BTW, you might be interested to see this ASHRAE table:


Quote:
Originally Posted by MN Renovator View Post
0.35ACH of ventilation either through forced ventilation or infiltration is quite a lot of air to move.
You might be speaking out of opinion rather than direct experience here. 0.35 ACH is actually quite difficult to achieve. I've been working on my house a long time now, and I'm not even close.

There was a previous post on ER, about some guy who was trying to get his house Passive House certified, and was not able to get it down beyond 0.6 ACH as I recall.

To achieve 0.35 ACH pretty much means starting before the house is built and planning in infiltration prevention measures from the very beginning.

In Europe, there is a big Passive House retrofit initiative going on and with energy costing 2X what ours costs, and all the years of Passive House practice under their belts, they have come to realize that the best retrofit efforts can only hope to achieve 0.65 ACH.

MN Renovator, if you actually had a blower door test done on your house, you might get some useful information.

The 0.35 ACH figure was from earlier Passive House work. The early efforts had gotten infiltration down to below 0.35 ACH and occupants were expressing displeasure with the houses because they felt so stuffy.

The fix was to shoot for 0.35 ACH, or less if possible, and then to supply 0.35 through HRV, with the input air flow balanced with the output air flow so as to not exacerbate the inevitable infiltration.

I have seen photos of German HRVs and they are about as large as a full-size cook stove.


In a discussion with the guy who currently heads up the Passive House initiative, he was asked about ventilation in general and HRV in particular, and how important were they.

His response was that a Passive House should start with a HRV.

BTW, those who are interested in this discussion should read the thread on DIY HRV is is a storehouse of great information.

Best,

-AC
__________________
I'm not an HVAC technician. In fact, I'm barely even a hacker...
AC_Hacker is offline   Reply With Quote
Old 04-22-12, 02:34 PM   #10
MN Renovator
Less usage=Cheaper bills
 
MN Renovator's Avatar
 
Join Date: Nov 2010
Location: Minneapolis, MN
Posts: 930
Thanks: 41
Thanked 113 Times in 87 Posts
Default

There is a difference. You've got two things mixed up.

ACH50 is the air changes a building goes through at pressure. Requires a blower door to measure.

ACH without the blower door will be lower, quite a bit lower.

Passivehouse, green, blue, red, purple, star, diamond, etc standards and comparisons are made at the ACH50 level. You need 0.6ACH50 to get to be a passivehaus.

This doesn't mean it's exchanging 60% of its air with all the doors and windows shut without the blower door in place.

Think about this. If I open my window and put my furnace 800CFM (48000CFH) blower into it and open all the rest of my windows, I'll only be at 2.73ACH. That's a furnace blower maxxed out, plenty of wind there!

There is a difference between a static air exchange through infiltration and forced infiltration with a blower door. The level of air exchange will not be the same.

MN Renovator is offline   Reply With Quote
Reply


Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT -5. The time now is 08:28 PM.


Powered by vBulletin® Version 3.8.11
Copyright ©2000 - 2020, vBulletin Solutions Inc.
Ad Management by RedTyger
Inactive Reminders By Icora Web Design