Ventilation options for green homes

This is a frequently asked question - what are the options for fresh air ventilation for Energy Star, Healthy Built, and LEED, and what are the pros and cons of each?

There are basically three options for fresh air ventilation - I'll offer a short description of each below and try to summarize the pros and cons that I hear most frequently discussed. While I would love to see everyone install an ERV, it isn't always feasible.

1) ERV (Energy Recovery Ventilator): This is a device that has its own fan that brings in fresh outside air and exhausts some air from the home. It can be tied into the home's HVAC ductwork, but it doesn't have to be - it can be separately ducted as well.

PROS:
Pressure-balanced system. This is mainly a concern for super-tight homes.
You know where the air is coming from (because you choose the location of the outside air intake).
Energy recovery recaptures some energy from the outgoing air.
The ERV fan has a smaller fan than the air handler (usually about 100W, but some new models are as low as 40 W).
Can work with non-ducted systems (like radiant floor).
Versions available with high-efficiency filters.

CONS:
Most expensive option - probably $1500-$2000 installed.
Some less expensive versions don't have timers or speed controls and may give you more air than you want.

2) Supply air only - This system involves a small outside air intake duct that connects to the return side of the air handling unit for the home. To qualify as a ventilation system, there MUST be an automatic damper in the duct and a controller. The controller is set to operate for a specified number of minutes each hour, and will cycle the air handler fan if it does not run for this period of time in any given hour. If the fan runs longer, the damper will close to avoid over-ventilation. The "air cycler" and a similar controller by Honeywell are the most commonly installed local versions of this system.

PROS:
You know where the air is coming from (because you choose the location of the outside air intake).
Intake air passes through the filter in the air handling unit, which could be high-efficiency. It's also a good idea to have a coarse filter right at the intake duct.
Since it uses the air handling fan, this also mixes air in the home to dilute pollutants. This can reduce occupant exposure to some types of pollutants (those emitted in occupied rooms).
Less expensive to install (~$300-400 typically).
Puts house under positive pressure. Some people feel that this is better than negative pressure, but the pressure is fairly small, and it's not clear to me that this is the biggest issue at play in our location.

CONS:
No energy is recovered from the outside air.
The air handling fan uses a lot of power (~300-400W), so it doesn't need to cycle for much extra time before a lot of energy is used. There is little additional cycling in many climates but because Asheville has extended periods of mild weather, there could be a lot of fan cycling here. This system uses the most overall energy of the three options.
Cannot be easily be used with non-ducted HVAC systems.

3) Exhaust only - This system involves using an exhaust fan that either runs continuously or on a timer to exhaust air from the home. There are bath fans available that do "double duty" as this type of fan (they run on a low, continuous setting all the time and then kick up to the normal flow rate when it's used as a bath fan). The fans have to be low sone. The Panasonic Whisper Green is often used locally; Broan/Nutone also has models that allow numerous fans to be controlled together to perform this function. There is also a switch called the "Smart exhaust" that will convert any low-sone bath fan to this function.

PROS:
Can be used with non-ducted systems.
Very low installation cost. Bath fans with this capability run approximately $150, and the smart exhaust switch is available locally for about $50.
Overall operating cost in our climate is relatively low. Although there is no heat recovery, the fan wattage is typically very low (10-20 Watts), so the overall energy consumption is almost as good as most ERVs.
Usually involves a bath fan upgrade, which increases the likelihood that the bath fan will function well as a bath fan and remove moisture from the home. Can be very helpful in densely occupied homes to keep indoor humidity levels down.

CONS:
Incoming air is not filtered.
Puts house under negative pressure. Some people don't want to do this, but the pressure is fairly small, and this is probably most important if you know the home has a problem crawlspace, etc. There are limits to how much air you can move at a time with this system in hot/humid climates, but it's usually possible to comply. Asheville is not considered a hot/humid climate. (it's mixed/humid)
No energy is recovered from the outside air.
You can't control where the air is coming from, so it is important to seal the house well from garages, crawlspaces, etc. A house with a lot of surface area that is attached to something like a problem crawlspace might not be a good candidate for this system.
The system does not mix the indoor air.

Energy Star media opportunity

For builders or buyers of Energy Star homes: the EPA is planning some media "events" for its millionth home celebration and want stories about Energy Star homes and the people who live in them. This is a great opportunity for some national attention.

http://www.energystar.gov/index.cfm?fuseaction=mil_homes.showSplash

RENOVATION tax credits and incentives

For existing homes, there are also credits and incentives. Here are links to sources of further information - read the rules carefully and discuss with your accountant if necessary. Be aware that in some cases, the home must be your primary residence.

Federal renewable energy tax credits (solar thermal, solar PV, wind, micro-hydro, and geothermal) and credits for installing new insulation, HVAC, windows, and more:
Federal: www.energystar.gov/taxcredits

North Carolina State renewable energy tax credits:
http://www.dsireusa.org/incentives/incentive.cfm?Incentive_Code=NC20F&re=1&ee=1

Progress Energy Home Energy Improvement Program: rebates for insulation, new windows, upgraded HVAC, and duct tightness testing:
http://progress-energy.com/custservice/carres/efficiency/programs/heip/index.asp

Summary of NEW HOME energy efficiency incentives

There are a lot of energy efficiency incentives for new homes out there - these are the relevant ones that I know of right now:

Federal tax credits:
(1) $2000 federal tax credit to the builder of a home that used 1/2 the heating and cooling energy of a home just built to code. Note that the home has to exceed Energy Star by a substantial margin, and that the credit is based only on heating and cooling and does not include water heating or appliances. The same process used to certify homes for Energy Star is used, but our computer program prints out a certificate for homes that qualify, and we present it to the builder upon completion of the project.
Note: congress is currently considering extending this and may add further incentives when they do so.
(2) Renewable energy: 30% federal tax credit for renewable energy systems including solar thermal, PV, wind, micro-hydro, and geothermal.
http://www.energystar.gov/index.cfm?c=tax_credits.tx_index (this site also has a good FAQ)

State tax credits - North Carolina:
(1) Renewable energy: 35% state tax credit for solar thermal, PV, wind, micro-hydro, and geothermal. There are caps on each, depending on technology. There is also a tax credit for passive solar homes that allows you to take a credit for a portion of windows, thermal mass, and control systems. However, the rules of the credit are very specific and homes MUST be designed with its requirements in mind to qualify. Also be aware that the total tax credit taken in a year can't exceed more than 50% of your total state tax liability - but you can roll the credits forward for up to 5 years.
http://www.dsireusa.org/incentives/incentive.cfm?Incentive_Code=NC20F&re=1&ee=1 (NC renewable credit overview)
http://www.dsireusa.org/ (links to incentives for all 50 states)

Local municipalities:
(1) City of Asheville: $100 permit fee rebate for Energy Star new homes. Additional $100 permit fee rebate for certified Healthy Built Homes.
(2) City of Black Mountain: $500 permit fee rebate for new Healthy Built homes certified at the Bronze level or better.

Utilities:
(1) PSNC gas company: $0.05 per therm rate discount for Energy Star homes, and $100 rebates for high efficiency gas furnaces, boilers, and water heaters.
http://www.psncenergy.com/en/residential-services/customer-service-center/rate-plans/default.htm#discount
http://www.psncenergy.com/en/save-energy-and-money/appliance-rebates/default.htm
(2) Progress Energy: 5% discount on electricity and a $400 rebate for new Energy Star homes with 14 SEER or higher AC or heat pump. The rebate is increased by an additional $300 per unit (max 2) for 15 SEER or higher, and an additional $600 per unit (max 2) for geothermal.
Note: 5% discount is to the homeowner, rebates go to the builder.
http://progress-energy.com/custservice/carres/efficiency/programs/ha/details.asp#faq
(3) Duke Power: 5% discount on electricity for Energy Star new homes.

Disclaimers:
When trying to determine whether you will quality for a rebate, pay attention to these things:
1) check with your accountant to make sure you will be eligible (you have to pay taxes to take tax credits!)
2) check the eligibility rules - we have heard that it can be tricky for owner-builders to take the $2000 federal builder tax credit. If something says it's for builders, an owner builder may not be eligible. We don't make the rules, we just provide the paperwork!
3) make sure the home you are buidling qualifies. Energy Star homes must be inspected throughout construction - once drywall is on, homes can't be certified.
4) We've done our best here to outline the pitfalls, but check each of the websites yourself to make sure you have current and accurate information.

Great progress energy workshop

For builders - there's a great progress energy workshop on Energy Star coming up. $40 to attend, and you get a $400 coupon you can use for a rating. Pass it on!

http://www.advancedenergy.org/buildings/courses/registration/es_pe/

North Carolina renewable energy tax credits

The state legislature appears to have just passed what will be a game changer.
http://www.ncleg.net/Sessions/2009/Bills/House/PDF/H512v5.pdf
First, they have renewed the 35% renewable energy tax credit for active solar, PV, passive solar, and other renewables. Coupled with the 30% federal tax credit (which now thanks to the stimulus has no cap for individuals), this is now a 65% off discount on these technologies if you pay enough taxes to use the credits.

The game changer is that they have also included geothermal for the first time. There is a cap , but it's pretty high ($8400 on the credit) so many small/medium systems won't reach the cap. At 65% off, the price of a geothermal system can look a lot like the price for a high-efficiency air-source heat pump. And a geothermal system with a water to water heat exchanger to replace a boiler system powered by oil or propane can look like a fast payback. I can't really just throw out numbers because different sites will vary a lot, but if you pay taxes, geothermal should be very seriously considered for both new homes and upgrades of existing homes.

There are also Progress energy rebates if you are in their territory:
Home Advantage (for new homes)
http://www.progress-energy.com/custservice/carres/efficiency/programs/ha/index.asp
and Home Energy Improvement Program (for existing home upgrades):
http://www.progress-energy.com/custservice/carres/efficiency/programs/heip/details.asp

SEE Expo presentation

This is for everyone who came out to see my presentation at the SEE Expo today - titled "Energy efficiency on a budget". We listed all of the things everyone at the office could think of that are easy and cheap and save energy, and we categorized them by how easy they are to do (couch potato, small effort/cost, medium effort/cost) and then estimated the carbon emissions reduction. Here they are in order with estimated tons of carbon and effort. They all add up to 10.1 (although everyone can't do all of them, and some would be double dipping), but the average car creates 6.3 tons of carbon, so you can easily take the equivalent of a car off the road. The "couch potato" ones add up to almost 1/2 a car!

Rank Item CO2 reduced (tons) Cost/effort
1 Insulate attic ceilings 1.5 medium
2 Heat pump water heater 1.4 medium
3 Don't run HVAC fan continuous ON 1.05 couch potato
4 Insulate floors 1 medium
5 CFL bulbs 0.7 small
6 Don't turn AC on and off. 0.6 couch potato
7 Clothesline 0.54 medium
8 Get rid of un-needed things (xtra fridge) 0.46 couch potato
9 Air sealing 0.4 small
10 Low flow fixtures 0.35 small
11 Kill phantom loads w/ power strips 0.28 small
12 Monitor power 0.28 small
13 Blinds/shades/trees on S, E, W sides 0.25 small
14 Close windows before running heat/AC 0.2 couch potato
15 Energy star appliances 0.19 couch potato
16 Turn down water heater 0.17 couch potato
17 Programmable thermostat 0.16 small
18 Pipe insulation 0.15 medium
19 Seal/cover attic fans, window AC in winter0.1 small
20 Keep garage door closed 0.1 couch potato
21 Turn down thermostat 0.053 couch potato
22 Fix attic kneewalls 0.05 medium
23 Lock windows to get better air seal 0.05 couch potato
24 Insulate hot water tank 0.04 small
25 Insulate + w-strip attic hatch 0.03 small
26 Fix water drips and leaks 0.001 small
27 Dual flush toilet conversion 0.001 small