Refer to local Building Regulations.

This is an area where consulting an experienced and qualified building designer will pay dividends.

There are devices called enthalpy heat exchangers, or energy recovery heat exchangers, for this.

I have an attic fan and open the windows at least once a week and run the fan. Early morning in the summer, late afternoon in the winter. A few minutes will do it. If the weather's nice outside, I just leave the windows open.

I have a sister that has a well insulated house and never opens the windows.........................her family gets sick a lot.

Your sister's problem is the problem I'm trying to avoid. I've been living in this heavily insulated house the insurance company is providing me. I've been here since Nov. 10. I'm beginning to get a running nose. I haven't had a cold or running nose in about 10 years. I take vitamin C, etc.

Another of my worries is mildew. Have you ever looked at a refrigerator that was turned off for a couple of weeks with the door shut? When you open the door, you see a lot of mildew. I just had to clean my camping refrigerator of mildew. What a mess it would be if your house got like that. Say, you left for a couple of weeks and turned the AC off. That one little act of trying to save on power could cause a monumental cleaning problem. Maybe, you didn't turn it off. Maybe, your wife did. It could easily happen.

I wonder if I could leave some holes in the wall near the eave and get natural air exchange? Of course, how big a hole and where and how many?

No matter what, bringing in outside air to create an air change will increase the heating or cooling load.

....and that's what local Building Regulations are there to provide against...

I'm not sure about holes in the wall. You should be able to do it all through your HVAC system................introduce a small amount of outside air, small micron filters on the returns, maybe even an electrostatic add on to pick up the tiny particles.

Some of the stand alone air purifiers work well also.

I'm in the same shape. This winter has been so warm, I think I've got allergies or something. Sinus issues for a couple of months now..............doesn't feel like a cold.

Curious!

Does the air have to be exchanged with the outside immediately?

Is it possible to store outside air (when temperature outside does not impact HVAC) in, perhaps, a compressed air tank?

When fresh is needed (perhaps a puff every hour or so), it can be drawn from the fresh air tank.

For that matter, is air fresher outside at certain times of the day (i.e. avoid paper mill smog in the morning)?

Just like water, the most abundant resource on earth, is sold for a $1 a bottle, how about selling bottled fresh air.

GA!

I have one similar (another brand) and it does a good job. I recuperate about 30-50% of the air energy.

It is very important to have a good air circulation. There are many pollutants that are slowly released by modern furniture, carpets, paint...

Some places even have radioactive gas (Radon) seeping in from the basement. Make sure that there is a good membrane below the concrete slab. The membrane should vent to the outside. It also reduces humidity infiltration.

Back in 1992 I lived in Vienna North Virginia. The house I lived in had double glazing, insulation, draft seals etc, quite cozy.....and an enourmous extractor fan in the ceiling of the stairway.

I queried this (strange to me) fan's reason for obviously being designed into the building's original structure and Radon gas extraction was the reason quoted.

House was refreshed, and chilly, after a couple of minutes of work. Your ears would pop when it turned on.

The ventilation problem seems to have been recognised for some time now. Are these fans still standard in new homes in the US?

My neighbor's garagedoor was insulated too. That seemed strange to me at the time but appreciated during bevvy sessions.

Adaptations......

To make a home really energy efficient it needs to be designed like a refrigerator cabinet with a light that stays on when the door closes. Like a fridge, you'll die in there if you get locked in.

I just described what the house had. Neighboring houses (same vintage) were identically equipped.

It seems that house design can't be fully passive in the US. Everything requires power assist. A little like US cars.......comfortable and inefficient.

Wal,

Unfortunately you are accurate in that statement. I believe, however, that we can design-in the necessary Radon prevention with methods that are fully passive (in the sense that they make use of direct solar or other energy sources instead of a fan). To my knowledge this has not been explored yet. It would make an interesting engineering or construction technology topic for a student to explore.

--JMM

I'm in the process of building a house. I specified a 95% or better efficiency for the furnace with a SEER of 16 or better for the A/C and 95% for the water heater (not a tankless though). Then the contractor got a quote on the foamed insulation (no formaldehyde) and I went for it.

Then the HVAC contractor tells me that I should spend an extra $3,000 to get an air makeup unit which connects into the air handler unit so there will be enough fresh air so I won't have "a sick house atmosphere".

Since all the bathrooms have vents to the outside and there will be a range hood vent to the outside I would think that I will end up enough exhausting enough air and that infiltration should take care of fresh air needs. But just in case I told the contractor to put in 2-6" vents and put covers on them in case I want to rethink it. I'm saving your link because I think that it would be just about all I would need to do it.

Thanks for the lead.

Yes, it's quite a problem. The fresh air needed to stay healthy must be treated, i.e, cooled or heated to a comfortable temperature. The more insulated a structure, the more air for air exchange must be treated. Of course, leakage air must be treated, too. The ideal would be to know how much is leakage and, then, add extra to make up the difference. But all of the air from the outside to facilitate air exchange must be heated or cooled (unless outside air is at a comfortable temperature). I don't think the super insulated house is a good idea. If the house is left unattended for a while with no air exchange, then, the whole house may be full of mildew. I may build a built in leakage by having a vent at the front of the house and one at the rear midway of the wall. They would always be open. What is the optimum venting and insulation amounts? I don't know.

Here is a link I found that might be of help;

http://www.inspectapedia.com/BestPractices/Ventilation_Whole_House.htm

Also found out that Broan makes several units with various capacities and configurations.

See: http://www.broan.com/display/router.asp?CategoryID=512

Spinco,

I have always been in favor of methods which are as passive as possible (independent of utility energy) and also as independent of the occupant's lifestyle as possible. Earlier designs of passive solar houses (think 1975-1985) often had the occupants tailoring their lifestyle to the needs of the house.

Regarding ventilation, I have often wondered about the possible use of a "solar chimney". That would be a vent, perhaps 4-6" diameter (or similar total area), that exits from a high point in the house and is integrated into the roof structure, so the sunlight on the roof is heating this vent, causing the air to be drawn out of the house. Then elsewhere one uses an earth-tempered duct to provide a source of make-up air into the house. The solar chimney would need some form of trap or very low-mass damper to prevent or minimize reverse flow (ideas anyone?). The solar chimney could be as simple as metal panning between two rafters on a south-facing roof, with the top opening under the continuous ridge vent and the bottom being connected back into the house.

Many air-to-air heat exchangers are made, and most of them have very attractive designs. I just don't like the idea of another mechanical component that will need energy to operate, periodic maintenance, and eventual replacement.

--JMM

I agree that something is needed to eliminate the human factor. The homes in my area already have a passive air exchanger (except for those that have the foam total enclosure). It is the attic, peak, and eave vents. They get a good exchange of air in the attic. This helps keep the attic from getting real hot in the summertime. Also, it helps heat the attic with daytime warmer air in the winter. It's mostly for cooling, though. If some of this air could be routed to the living area, that would be great. However, regulating the amount would be somewhat of a problem without thermostatically controlled dampers, etc. The more outside air that gets into the house means more air to heat or cool. That negates the efficiency of the heavily insulated house. If the fan of the AC/heating unit ran all the time, then a measured amount of air could be let in and out and a constant change of air could be obtained. Of course, the running of the fan would increase the electric bill. To get a constant exchange of air, I believe a continuous running small fan will have to be used. I've seen some advertised that connect to the AC and have inlet and exit ducts. I believe that's what I'm going to use.Thanks for you comments,Have some fun today,PAPADOCRMFR

Papadoc,

Good to see you following-up on the thread. My post didn't clarify the passive solar exhaust of air from the house. I should have noted that the "duct" when it exits the living space remains separated from the attic's air, probably by panning or a similar barrier placed between the rafters or top chord of the trusses. I read your comment regarding the attic ventilation to do two things--help to cool it (as you wisely said), and also to remove any build-up of water vapor that has moved through an imperfect vapor barrier from the house into the attic.

--JMM

They make what they call trickle vents that install on the window frames. They also make a vent that you can install in the wall. They all have dampers that you can adjust the air flow. You can also get vent installed on HVAC. Installs on the intake of the blower and also has a damper control.

Here is a link to what they call trickle vents on windows. http://glazpart.com/glazing/pdfs/standard-vent.pdf

Thanks. I looked that up and I couldn't find any here in the US. It seemed they are used mostly in the UK. It looked like a good idea to me. Install them and then, don't worry about them unless you encounter a super cold night. We don't have much of that here. Nowhere did I see how to design them, i.e., how many and where.

I prefer items that require no maintenance or remembering. I'll probably have to have something with a little duct work.

Thanks for your help,

Have some fun today,

PAPADOC

RMFR

Hello - I assume that living in Texas the heat in summer is causing most of the cost to aircondition your house. To reduce your energy bill and get cool air from the outside I saw some interesting approach - not really knowing it will work in your location - the guy installed a U shapeded PVC Airduct (around 1,5 feet diameter) which ran from the intake point 40 feet away from the house, at first down to around 6 - 8feet in the ground and then 40 feet into the house. This reduced the intake air temperature already by 5 to 6 degrees. This amount you will not see on your energy bill. For him it worked also in wintertime as the duct runs already in a zone where the temperature is constantly around 7 to 10 deg.C and no frost can be found. So the incoming air is also a bit heated up. But in wintertime the fan is running at a lower speed to allow the air to pickup the heat. Naturally you need a good air intake filter as the pipe is difficult to access and clean.But a rotary air heat exchanger and the heatpump assembly he is using anyway solves this problem.

What you need is a heat pump where the stale air is drawn out of the house & passed over a radiator similar to a vehicle rad that takes the heat out of the stale air and heats up the replacement air being drawn in, this is a simplified explanation of how they work, the actual opperation is more complicated but does exactly what I've said.

Bazzer

Open the windows and dress for comfort.

It really seems in this new day and age the new homes being built by contractors has a selling point of the amount and type of Insulation without any concern for the people living within. I am a oxygen deprived person and must have fresh air. I can walk into a home that has stale air and have to leave. Beautiful, well kept, no pets,no smokers, Just no oxygen in the air to breathe..Meters, programed oxygen sensors, and fresh air duct fans and vanes have been used in commercial buildings for eons and must be installed in the newer tightly insulated homes. These assure the home has a percentage of the air is exchanged constantly to assure the oxygen level is maintained..

Use an energy recovery ventilator to reduce heat loss and gain to ventilation and an "earth tube" (ventilation pipe buried underground) to temper incoming fresh air.

How many occupants are there? What is commonly done is you install an Exhuast fan and Gravity louvers which automatically shut-off when the induced draft exhaust fans are off.

Ventilation depends on the number of occupants and the activity you have with in a room, say kitchen or comfort room for instance needs greater amount of air exchange compare to your bedroom. I bet you can not consume all the oxygen for respiration with a room size of 2x2.5 sq.m. so air exchange will be as minimal, thus also the fan size. There you can have an heat exchanger type-recirculated, air-split type aircon unit.

You can also have it automated, installing timer relay to power on & off of your ventilation with in a day.

You could even design a ventilation by natural convection. Hot air rise cooler air below. You could use the heat in your ceiling to heat air-as it escapes your vent it will cause a flow if you provided some vent below. Cool right?

You might also consider checking "Angie's List" for qualified local Consultant service providers...

Friends,

I prefer the method mentioned by uli newBuilder and VillageTechnologies. I have described my experience and recommendations on this in a few forum threads in the last 2-3 years. I shy away from the heat recovery ventilators solely because they introduce an additional area of maintenance. (The ones that exchange moisture--"enthalpy"--are worth looking at.) If your earth tube is sloped so condensation will drain, is smooth-walled and without holes; then mildew or molds should be minimal and radon will not intrude. If its indoor end terminates in the return air side of the air handling unit (the "cold air return"), then the house will be slightly positive in pressure compared to the outdoors whenever the fan is on, so air leakage points will be exfiltration instead of infiltration. Whenever you run a ventilation fan (bathroom, range hood, clothes dryer), the make-up air will be modestly tempered by the earth contact and will be diffusely distributed throughout the house through the duct work, so there are no cold drafts.

Beyond this, I suggest that you seriously investigate ICF's (insulated concrete forms) for the exterior walls. They will isolate your house from the outside and from daily temperature swings. This will allow you to put your central HVAC system onto a time-of-day schedule so you could qualify for off-peak energy rates (if not here they are coming soon even to residential customers). My daughter's house has had a heat pump failure and it took them about 2-days to realize that it had happened (outside temperatures were quite uncomfortable at that time). ICF's also give you exceptional insect/mold/mildew/fire/tornado resistance and essentially zero air infiltration. You can allow 10-25% more cost for the outside walls, compared to typical construction, but if you compare to the cost for equivalent resistance to fire/tornado/energy-loss, the cost is less than conventional. In comparison to SIP's (structural insulated panels), ICF's are significantly more $ and time, but again the mold/mildew/fire/tornado resistance still favors ICF's. For roofs, you can easily and very cost-effectively design in structural ties between the ICF walls and the roof assembly to give wind uplift strength capable of resisting any wind load you want to consider (and this is much easier than if you are doing conventional construction).

Your area is primarily a cooling area with only modest winter heating, but with occasional severe dust problems (I believe). Your lowest HVAC cost is with a ground-source heat pump (but be prepared for a cost/payback of about 10-years and lots of disagreements with the HVAC contractor when you say that 18,000BtUH is more than you need). With an earth tube, ICF's and at least R-50 roof/ceiling insulation, proper use of shade to exclude summer direct solar gain, and a ground-source heat pump, your annual HVAC costs should be less than $300 on a 1500 sq.ft. home. If you want lower costs, then zone the home. However, with ICF's, the temperature swings over a 24-hour time are so small that I (contrary to conventional wisdom) do not recommend the use of a typical set-back thermostat. Probably in the next 5-10 years we will see increasing availability of zero-energy homes and off-grid designs (Davis, CA is one place where these are being worked on).

--John M.

A good method is to wire ventillation fans to an outdoor thermostat. Whenever the outdoor temperature is within the range that you preset, say 70 to 75°F, the fans turn on and pump in lots of fresh air without any need to heat or cool it. Most of the year the fans will turn on automatically like this for at least a few minutes every day, but you may need to use the manual switch occasionally in midwinter. Ask your HVAC comtractor if this is a standard option with your heat pump. Running the bathroom exhaust fan also causes a little fresh air get sucked in.

Your idea sounds real good. I really want something that requires minimum or no maintenance. Having some vents that stay open all the time might work. But, how many and what size?

Does anyone know of a system that simply runs a small duct from the outside to the inside return air duct? This would supply outside air continously. The air would escape through cracks or planned openings. This would be like a room air conditioner that cools with fresh air only. Of course, there would be a loss in efficiency. If no one has done this, sizing the ducts and openings may require a trial and error solution. This would be the simplest solution. There would be no new moving parts except for some manually operated dampers to close or adjust the system.

What do ya think?

Have some today,

PAPADOC

RMFR

In studying passive solar heating design some years ago, one thing that became critically important was ACH (air changes per hour). You have to have them and the number varies by size, volume, number of occupants, relative humidity, etc. The most efficient and effective way to do this was an air to air heat exchanger. One with no moving parts. It will heat up the incoming air in the winter and cool it down during the summer. I would have a competent person calculate and spec a specific exchanger for you so you do not over or under size the exchanger. Your HVAC system will control the humidity in the summer. If the air falls below 50% in the winter you can boil a bit of water to bring it back up (assuming you do not have a humidifier in the HVAC system).

HVAC stands for heating, VENTILATION, and air conditioning. Some cheap systems omit ventilation, but any complete HVAC system has it built in. The only question is, when do the vent fans turn on? Obviously heating and air conditioning have to be controlled by an INDOOR thermostat, but having ventilation controlled by an OUTDOOR thermostat saves energy. Ask the heat-pump manufaturer or contractor if that is a standard option with their equipment.

Hey, that's what I needed to know. I'll check that out with an air conditioning company.

Thanks,

PAPADOC

RMFR

Commercial buildings pull and mix outside air with recirculated air, as required by commercial building codes and laid out by ASHRAE standards. However, residential homes don't normally pull outside air in. Ventilation (in HVAC) does not necessarily mean coming from the outside. You don't want a significant volume - certainly not the volume that flows when the heat or AC comes on - coming from the outside. You only need something on the order of a 1/2 ACH. Typically in the past there was enough leakage in the building envelope of a home that having enough fresh air was not an issue. Keep in mind commercial buildings are typically running all the time, whereas residential systems are not.

Hi PAPADOC,

I sealed up my old house by caulking, glazing, painting, replacing doors with new tightly weatherstripped ones, some new windows, blown attic insulation (there was none), and a few (ok several) cans of expanding foam, and the air in the house became like the air in a bowl turned upside down on the ground. A vapor barrier (there was nothing there either) on the ground and a few more foundation vents helped immensely, but my goal is zero air infiltration from the crawl space.

My solution/goal is to create positive air pressure (filtered and heat exchanged) inside the living space to prevent air from coming in from anywhere else. I have yet to implement this but in my research I learned a lot. I found this page has lots of information about air exchange. Hence the name, 'Whole House Ventilation Design Guide'. There's details like how many cfm of air to move, etc.

Everybody,

The above link is just one page of a comprehensive site about the buildings we live in, the problems they can have, and how to fix them. It's called Inspectapedia, I think everybody who lives indoors, ought to at least have this one bookmarked.

While we all worry about the money spent on heating and cooling as we should, energy is running higher no matter what fuel is used. As we note on the window and through the wall airconditioner and heat pumps is a fresh air door opened and closed with a switch..With the tightening up of the homes it is demanded you use a likewise system in your central Air and heat Unit. An open window works great for that area but not the whole house..Do you need one..spend a little, $30 and 'google' a Finger Oxygen meter...Below 90 you need fresh air. Night or day the question here is your health. The pocketbook comes a bit later..

If you want to go with radiant floors, and a good passive design, (heat only what is touching the floors) they like to always stay at the comfort zone temperatures, even when air exchange is happening, the floors maintain their heat much longer. (convective heat systems stratify the air in the house and send the warmest air to the top, where it's not needed ). Insulation and airtight construction are the best way to conserve the heat in the house, and filtered air exchange is a must. ( or a well designed cross ventilation system). The humidity in the house (radiant floors do not emit humidity) and crawl space should be monitored and dealt with, so and average is maintained. Since insulation and airtight construction have no moving parts to maintain, it's a wise investment, and the new soy oil expanding foam insulation is allot less toxic. ( no out gassing ) .