Whatever goes out has to also come in at another location. When air exits because a bathroom or kitchen exhaust fan is operating or the exhaust from the combustion vent from your furnace or water heater, that amount of air is being replaced in the interior from elsewhere. If your house is tight and there's no makeup air system, that means that air leaving your range hood is being replaced by air coming from a backdraft on your furnace/water heater exhaust (which is dangerous), or coming down the chimney, or through other vent openings not operating. If you house isn't tight, the make-up air can also flow through those same sources but also through the wall openings (like sockets), the floor, around windows, door gaps, up from the basement, etc.

Building codes only have to do with new construction. If your house was properly inspected when it was built, it complied with whatever the requirements were at the time. Changes to comply with new requirements aren't usually mandated except sometimes to a limited extent when significant remodeling is done.

We were issued a certificate of occupancy less than a year ago with multiple code violations: dryer duct length, no exhaust damper flap, exhaust hood type with screen (not allowed per code) - FIRE HAZARD, range hood duct size, range hood exhaust - no make-up air, main air return in kitchen 5’ from double-ovens and less than 10’ from 1200 CFM exhaust hood, smoke alarm 6’ from double-ovens, no outdoor air at a continuous rate (whole-house ventilation), duct insulation code violations, indoor combustion air code violations, required heating code violations…etc.

Our building inspector, said they rely on builders and their subcontractors to comply with code and manufacturer installation instructions. They will not get on ladders to look at duct sizes, R-values, or measure duct length…etc. I have gone through each code violation with the building inspector, and they do not deny any of the violations.

The only one I have not gottten full clarification on is M1505.4.3. (“The wholehouse mechanical ventilation system shall provide outdoor air at a continuous rate”). The building inspector agreed this code applies to our home (with < 5 ACH50 air filtration rate), and should be followed. However, this seems like a huge ”miss” by our builder, their HVAC contractor, and the inspector. The only way I see to meet this requirement is with an HRV or ERV. How do you miss that? It’s a big, visible, ventilation system that does not exist in my home.

Is there any way an exhaust-only ventilation system, such as our continuous powder room fan, would meet the 2018 IRC requirement (M1505.4.3)??? I don’t see it. Or is there a less expensive, low-tech way to provide ”outdoor air at a continuous rate” other than and ERV / HRV?

It’s a lesson to everyone out there that believes the building inspection process will be a safety net for you. It will not! We have learned the hard way.

Interesting. I haven't ever had a house built but I've never heard of a Certificate of Occupancy being issued when a structure has code violations that need to be fixed. Usually it's withheld, to hold as hostage to be sure the fixes are done. If they do that, why bother having inspections at all?

I've had permits pulled for various types of work, including additions, and I believe in my area, a house gets red-tagged (occupancy not permitted) if the permit isn't closed out by with a final inspection within a reasonable amount of time.

You need some serious help from new tradesmen to get this stuff fixed. And, you may need to speak to a lawyer too, it sounds like you paid for substandard work that may have violated the terms of your contracts.

Good luck.

Thanks so much!

I guess during the housing boom 2020 and 2021, Indiana adopted new code (IRC 2018) and no one was properly educated or trained from building inspectors to GC’s and subcontractors. The inspector who ”passed” our house no longer works for our city...maybe he was incompetent. The ”new guy” has been very helpful fielding all of our questions, but the damage is already done.

We live in a suburb of Indianapolis. This isn’t some remote country town‘s building inspectors.

We’re doing our best to figure out next steps. That’s why I’m also reaching out to experts on this site for their expertise and knowledge of HVAC building codes: especially that outdoor air requirement in M1505.4.3 that my city inspector has not been able to fully explain to us. The energy company that did the blower door air infiltration test claims the exhaust-only ventilation system (continuous bathroom fan) meets the 2018 IRC code requirement. I don’t see how that meets the M1505.4.3 code that says ”shall provide outdoor air at a continuous rate”

As I read this, "outdoor air at a continuous rate" is handled fine with an exhaust fan. As Elmer said, what gets removed has to come back in and the only option is outdoor air. It would seem pretty simple to run a fan installed backwards (obviously not in a bathroom) to comply if they don't like it. You could tee it in to a supply register somewhere so you don't have to cut into drywall.

An ERV/HRV is a way of getting fresh air that is partially conditioned. You do not need one or the other to get just fresh air.

I have to agree that is a shocking amount of violations to allow a CO. It puts you in a tough spot. I had a few things but they were silly ROW stuff.

Make up air is a totally different thing but it sounds like you understand that. Mine is from a damper on the air handler. Not that it works all that well but I am all electric so less of an issue.

The air infiltration limits are established to ensure performance of the building thermal envelope. Air leakage for newly constructed homes in Indiana should be less than five air change per hour when measured by a blower door test at a pressure of 50 pascals or 5 ACH 50. That limit triggers the need for mechanical ventilation in accordance with section M1505.4 of the code. The ventilation rate can either be continuous as per M1505.4.3 (1) or intermittent as per M1505.4.3 (2)

The need to install a make-up air system for your range vent hood, your furnace combustion air and water heater combustion air are both important and governed by other sections of the code.

There are a variety of ways to meet the code requirements for mechanical ventilation. I suggest a balanced strategy utilizing an HRV to bring in fresh air and exhaust an equal flowrate of stale air to meet the rates in M1505.4.3(1) (continuous) or M1505.4.3(2) (intermittent.) This is separate from any combustion make up air or range hood exhaust make up air required.

Thank you @Charles Ross Homes! Do you disagree that the outdoor air requirement can be met by an exhaust-only ventilation fan (our powder room continuous fan)...that the outdoor air seeping in through cracks and openings in our home meets the requirement of M1505.4.3??? Do you see any interpretatin of the code that would allow the exhaust-only continuous bathroom fan to meet the 2018 IRC requirements?

Ultimately the interpretation of the code is up to your local code official.

An exhaust-only ventilation strategy relies on air leakage. It brings unconditioned air into the living space. It has the potential to depressurize a space, which, given your lack of make-up air for combustion appliances could contribute to back drafting as Elmer noted above. It's not a good strategy.

I suggest you take a look at Panasonic's Whisper Comfort ceiling spot ERVs. You can purchase them starting at around $450. Make sure the size selected meets the requirements for your home per M1505.4.3

I am building a pretty tight house. So to get fresh air intake into the home I will install 3" pvc pipe in an outer wall. Have an elbow at the top pointing in and another at the bottom pointing outdoors. This will allow fresh air as needed to balance out any pressure differentials. I will also install a mechanical induction fan in the fresh air pipe so it has a mechanical option. Also will have automatic humidistats in the bathroom exhaust fans to control moisture. When they turn on they will pull fresh air in to the home through the pipe. Fans on the ceiling that draw up so that the interior air continues to mix .

Air balance is very important to controlling the moisture movement in your home.

If you have central heating with hot air ducts. I put a temperature controlled shuttle that has a 4" pipe to the outside and connects into the return air duck as it enters into the furnace. This draws fresh air in even when the furnace isn't running as fresh air will be pulled in the ducts. Balancing the interior air pressure. A slight exhaust pressure inside your home will help keep the air in the house fresh. And help you stay healthier

Good luck hopefully there is something there that helps, someone

The system described by aklogcabin above would not meet the 2018 IRC code requirements without a blower and associated controls. If your air handler is variable speed and has an appropriate turndown you may be able to use it in lieu of a separate fan, but you'd need to modify the system controls for that purpose.

Yes I described a passive system. So CRH if an induction fan controlled by a humidistat was added to the air handling system would this suffice

No. Humidistats are for controlling indoor relative humidity. When coupled with a bath vent fan, a humidistat will control relative humidity in the bathroom only. The code is quite specific that a fresh air ventilation system needs to be mechanical (i.e., a fan for moving air) and introduce air either continuously at the stated flow rate or intermittently at the stated flow rate for the particular on/off frequency. I would not install the system you've described for a home in a cold climate like Alaska.

Fresh air ventilation is a somewhat tricky thing. You don't build a tight house just to put pipes in the walls to let fresh air in.

And there is more to fresh air then humidity. Mostly, humidity changes too much or is an uncomfortable range outside and inside needs to be more stable and often different.

In my climate and house, humidity is best controlled inside with near zero air changes. In a smaller house with more occupants per SF - it might be too humid. In a climate like AK, that may strongly favor bringing in some air all the time to dry it out. But that isn't the case in every situation or climate. Anything with just a pipe would be changed by wind which is not want you want to do which is why a fan is needed.

In my situation, ventilation is more for smells and removing CO2/VOCs/etc for which we have an intermittent bath fan.

ERV?

I agree with was written. In the house we like in. I have a 4" pipe going to the outside air connected into the return air plenum at the furnace connection. It has, had, a bi-metal temperature coil in it to close off outside air in cold months. I removed it for several reasons.

Most thermostats are mechanical control and can be used to run the fan only. Which will draw fresh air in mechanically. I have a 2 story house with crawl space. And each room has registers, usually 2 per room. My thoughts behind just having a 4" pipe to outside air connected in the return air plenum is that fresh air will constantly be pulled through the fresh air intake into each room through the registers. And maintain a neutral inside pressure.

Every time a door is opened or bathroom fan comes on fresh air is drawn into the home creating a passive fresh air supply. Or use the thermostats fan controls.

Hey maybe I'm all wet but our home is doing well after 30 years.

The discussions on whole house ventilation, R value for w

alls and home appliances is interesting and fairly new. And I'll be the first to admit that I'll always br trying to push the envelope n get better. At least in my mind

As for the bathroom vents. I had an energy audit done. After the blower door test, which the technician said was one of the tightest he had tested n tested it twice. His recommendation was to install bathroom vents with automatic humidistats in them. Guess that stuck with me as the doors are usually open anyways.

Interesting discussions as fresh air ventilation is something I have thought about because my house is airtight. Our new gas furnace is a condensing type that has pcv pipe through outside house foundation wall to bring in fresh air for combustion. Can this pcv pipe serve the purpose to pull fresh air into the furnace—>ductwork—>vents to replace exhausted air from the bathroom fan without opening a window when the furnace is off? And is it ok when the furnace is on (burning natural gas) while the bathroom exhaust fan is on pulling air out?

"Can this pcv pipe serve the purpose to pull fresh air into the furnace—>ductwork—>vents to replace exhausted air from the bathroom fan without opening a window when the furnace is off?"

What you've described is a condensing-type furnace which is a sealed combustion device. It has a dedicated combustion air supply and exhaust. It should not be affected by the operation of bath vent fans in your home. Consult the manufacturer's installation instructions for your specific model. I doubt they'll endorse tapping into the combustion air supply for other purposes.

A couple of other recommendations:

If you need a whole-house mechanical ventilation system to meet code, then do it properly with one or more energy-recovery ventilators or heat-recovery ventilators sized for the application and in compliance with the applicable code (s). A system which controls indoor relative humidity is just that; it's not a system for meeting whole-house ventilation needs.

To control indoor relative humidity, install appropriate ventilation fans to deal with point sources of moisture, e.g., range hoods, and bath vent fans. Where the exhaust flow rate from those devices requires make-up air to meet code, you need a properly designed make-up air system. Ensure your air conditioning system is designed to provide adequate dehumidification. Depending on your climate zone, consider supplemental dehumidification during shoulder seasons when no air conditioning is being called for. Many dehumidifiers have options to provide fresh air ventilation.

OK, I have a new issue related to our "whole-house ventilation" that we have been discussing.

Our continuous powder room fan (exhaust-only ventilation system that does not meet Indiana Code for "shall provide outdoor air at a continuous rate determined by table" M1505.4.3) is "y-ed" into another full bathroom exhaust fan - all 4" QuietFlex flexible duct as it exits through the roof of our house ~ 35' run...

We just discovered the Broan continuous exhaust fan is 110 CFM and requires a 6" duct. The other bathroom fan is a Broan "can fan" 70 CFM which requires a 4" duct. I would think the "combined" duct would have to be larger than 6".

Also, when one fan is running, air comes out of the other fan - exhausting INSIDE our home. I sprayed air freshener in one bathroom with the fan running, and my husband could smell the air freshener coming through the exhaust fan (off) in the other bathroom. When we took the cover off the powder room fan (with fan off) and ran the fan in the other bathroom; there was enough air forced into the powder room to cause the fan to spin. When we turned on the powder room fan, we could watch the fan slowly change direction as the powder room fan began to exhaust air.

We found the same situation in our Master Bathroom, where the toilet room fan and the shower fan are "y-ed" together before exhausting out of our home. Again, we could feel air coming OUT of the shower exhaust fan when running the toilet room fan and vice versa.

How messed up is this? Exhaust air is not allowed to recirculate back inside the home is it?

If two 70 CFM exhaust fans are supposed to use 4" ducts, wouldn't you need to increase the duct size if you "y-ed" them together...if doing that is even allowed?

Is it time to move forward with a legal claim against my builder for breach of contract? We have found over a dozen code violations!

I like to install bath vent fans with dedicated exhaust ducting to the exterior of a home to prevent the type of issue you have. The exception would be where a heat-recovery ventilator (HRV) or energy-recovery ventilator (ERV) is configured to exhaust air continuously from multiple baths or where an in-line (axial) fan is configured with multiple inlets and serves more than one bathroom. In either of those cases, exhaust flow from one bathroom would not be introduced into another. Instead of messing around with duct sizing and backflow prevention dampers, I recommend you simply install a dedicated duct for each fan.