The HVAC installer should have spent the modest amount of money to run the PVC intake to the exterior wall. I would not be surprised if you find other installation issues with the furnace an hot water heater. Investigate it is possible to add the exterior intake.

My other suggestion is to call the code official and have them pull out the inspection report for your HVAC installation. Ask what are the minimum venting requirements and if they were checked during the inspection. If there is a code violation you need to have the builder correct this during the one year warranty period. Insufficient combustion air is a serious problem and needs to be addressed.

Thanks so much for the information.

We did just find other code violations. Our ducts running through our attic (unconditioned space) are R4.2 and R6. I was informed that supply runs need to be R8 and returns need to be R6. Is this correct?

We also found the incorrect zone dampers installed. We have unequal zones 250 sqft. and 750 sqft. We were told we need a bypass duct or relief duct with current dampers. Or, we need to switch to dampers that will open partially to relieve the excess pressure. We were told our coil will freeze or blower motor fail with the current design. Again, this is probably not a code thing, so I'm not sure how we can demand the correct design.

We just learned that we only have a single stage AC unit and we negotiated a 2-stage.

Also, we have 4 - 90 degree turns in our main trunk / plenum with HARD 90 DEGREE INSIDE CORNERS. I don't believe there is any code violation here, but we have been told this creates a large degree of air turbulence and should never be done.

We have also been told that our returns are not sufficient. UGH...not sure where to go from here.

Also, can you clarify the requirements for the exhaust pipe for the furnace and the hot water heater? We were told they need to be 3' from each other - and any other opening into the house - 4' from a gas meter - 2' from a condensor unit. Our hot water heater exhaust pipe, furnace exhaust pipe, and bathroom vent are right next to each other in a row...just a few inches apart. Any clarification on this code requirement would be greatly appreciated - I cannot find anything online.

There is no way for us to help you need to take this up with the installer and the town inspector who knows your code in your area.

Sounds like you have powered vent appliances that direct the PVC pipes out the sidewall. If so, then you follow manufacturer's directions, not the calculations for inch/BTU on natural draft appliances.

I am not sure if the insulation values of the ducts installed in the unconditioned attic are code violations. This is another item you need to discuss with the code official.

The other items fall under the category of poor installation practices and not providing what was in your purchase agreement. You need to put all of this in writing and give it to the builder ASAP. If you used an attorney to buy this house I suggest paying for some his/her time to advise you how to proceed. The builder will try to stall to run out the clock on the one year warranty. I was skeptical that a new build house would need a 100K BTU furnace. An oversized furnace with small zones is not going to work well. I assume you requested a 75 gallon hot water heater.

The manufacturers usually specify a 12 inch minimum distance between furnace intake and exhaust. The distance to a window which can be opened is usually 3 feet. The distance to the gas meter is likely to be a code requirement. The exhaust should be high enough to it will not be covered during a snow fall.

In my area, building inspectors are usually too busy with their work to answer anything other than brief questions. They tend to tell individuals that they need to call a licensed contractor for information. Also, as has been pointed out, what constitutes a technique or a material required by the code versus inept or ill-advised workmanship and material choices that would have been better if done differently are completely different matters. An inspector will have no useful information to provide concerning choices and techniques that are outside the sphere of code requirements.

That aside, it sounds like this person may not have had the best job done nor done to specs that were stated and paid for. I think the starting point would be to find a licensed HVAC contractor willing to spend a few hours (to be paid at the normal rate) to inspect the situation to give their professional assessment.

Good luck.