I'm assuming the bedrooms have supply ducts and registers. A return register connected to a duct can be located high on a wall or above the entrance door. It depends on where the ducting for the rest of the return air is located to connect to. Where is the closest return air register? Can you access that duct system?

There is only one return register for entire unit and it is very far from the bedroom. I just don't know the architecture of return register. Does it require its own deducted ductwork?

Conditioned air supplied to various rooms in a home needs a clear path back to the air handler where it gets reheated or re-cooled and recirculated. It appears your system has a single, central return. In that case, the return air flow path from bedrooms is typically the gap between the floor and bottom edge of the door. Those are typically small areas which limits air flow and compromises comfort.

You may be able to install return ductwork if there is a basement or crawl space below the bedrooms or attic area above. If not, you can install transfer grills or jump ducts to enhance air flow to the hallway when bedroom doors are closed. Those will improve comfort, but at the expense of privacy.

Thanks Charles. What could be the reason why the original installer did not install dedicated return ductwork when they updated these in 2004? Still not a thing at that time? I have neighbors up and down.

While I consider installing a return in each bedroom to a best practice for any forced air HVAC system, there is no such requirement in the residential mechanical code. HVAC contractors --and the builders and remodelers who employ them--competing on price will often do only what is needed to comply with code and minimize cost in order to be awarded the contract.

Charles, thank you! Due to water damage, my unit's ceiling and above neighbors floor is opened. Can I take advantage of this time to install return ductwork? Ballpark estimate for a 800 sqft unit?

If you have easier access, it's an ideal time to retrofit ductwork and to improve insulation and air sealing, too. Costs will depend on the extent of the new ductwork and how difficult it is to integrate it with your existing system. I recommend you consult with a couple of reputable local insulation contractors and HVAC contractors to get pricing. Make sure the contractors are licensed and insured, and that they obtain any necessary permits/inspections required in your area.

Unless you are having an issue with unequal temperatures in different rooms, leave well alone. The system was designed to either have a central return or a return in each room.

It's a fair point that you don't need to make changes if you don't have performance issues. That said, assessing system performance vs. design involves more than measuring room-to-room temperature differences. For example, a really well insulated home might show minimal room-to-room temperature differences, but be lacking fresh air ventilation.

There is perceivable temperature difference between living room and bedrooms. Thermostat is located close to furnace which is in living room. Bedrooms are located down the narrow hallway one on each side. I am assuming just installing a new thermostat on bedroom will not do the trick

Ensuring occupant comfort in multiple rooms (which may be on multiple levels) when the HVAC system is controlled by a single, centrally-located thermostat is a tall order. Enhancing return air flow from the bedrooms should improve comfort and air quality. You might also consider replacing your current thermostat with a "smart" thermostat which is able to accept input from multiple remote sensors and control temperature based on a program. For example, daytime control might be based on the temperature sensor in the Living Room and nighttime control on the temperature sensor in one or more bedrooms.

Charles, thank you again for wonderful input. I have Google nest which I believe is a smart thermostat? How much work does installing remote sensors require?

Since my HOA doesn't allow exterior condensers, mini-split is not an option. I am looking at PTHPs.

Remote sensors are low-voltage and should be easy to install if your ceiling has been removed.

PTHPs will require venting to the exterior so make sure they're okay to install. They would eliminate the need for ductwork altogether.

"My bedrooms...do not have return air vents."

Just to be clear: return ducts carry air to the furnace while supply ducts carry conditioned air into rooms. What would be gained by adding a return duct to a bedroom? I could understand adding a supply duct to a bedroom if it didn't have one.

How much work does installing remote sensors require?

Google Nest Temperature Sensors connect to a Nest thermostat via blue tooth and a powered by batteries.

• How to set up and install the Nest Temperature Sensor in the Google Home app

Charles, I got bad news today. HVAC professional looked at my current HVAC setup and he confirmed that there is no way him or any other company can add return ducts. I am back to square one.

Mini-splits that require exterior condensers are also not an option as HOA forbids them.

I will add nest sensors but I don't think they will completely solve my temperature differential issue.

Any other suggestions?

As noted above, there's more to HVAC system performance than minimizing room-to-room temperature variation, particularly in bedrooms where poor air flow can result in unhealthy levels of indoor pollutants such as CO2. Air supplied to living areas needs to be balanced by an equivalent return air flow. Absent dedicated return ducts in the bedrooms, you can improve the return air flow by increasing the area of the space under each door (undercutting,) installing transfer grills (essentially an opening in the wall between the bedrooms and hallway) or jump ducts (which consists of a grill in the ceiling of the bedroom connected to a grill in the ceiling in the hallway by a short section of duct.) At least one company makes transfer grills you can install in doors https://www.tamtech.com/product-category/transfer-grilles-rap/?srsltid=AfmBOoqyqRqk2NX86z3KDSzGCkmGiGgZuS7-DXyo8vn9pQpJCWgGeUGB You could also do a combination of these alternatives. While any of these will improve air flow, they will also compromise privacy. Good luck.

Even if you can't install a full return duct - maybe installing a transfer grill that increased ability for air to leave the bedroom with a closed door and get to the centrally located return - as Charles Ross Homes states. We did a transfer grill in an upstairs bedroom for this very reason. It's rare to have a return in each bedroom.

@Charles Ross Homes @just_janni I am not clear on transfer grill option. We always keep our bedroom door open. What good would a transfer grill do that an open door is not able to do?

If you don't close the bedroom doors you don't have to worry about a return air flow path, but you don't have any privacy, either. You also have no barrier to smoke/heat propagation in the event of a fire. You might improve the comfort level by installing balancing dampers in the supply duct work. They can be adjusted to help direct more air flow to the bedrooms.

Kiran K: "There is perceivable temperature difference between living room and bedrooms."

Have you adjusted register dampers to help with the temperature differential? For example, if the bedrooms are colder, open their dampers further to allow more warm air into those rooms and close the living room damper somewhat to reduce the flow of warm air into that room.

@wdccruise I have not tried adjusting the registers. Is it just a matter of adjusting the knob pointed by red arrow?

"Is it just a matter of adjusting the knob pointed by red arrow?"

Yes. As you move the knob, watch the louvers inside the register to make sure you're opening or closing the register as expected.

Inexplicably, airflow (when fully open) through my registers varies dramatically so I've had to open some of them all the way while closing others part way in order to roughly equalize the temperatures of the rooms in my condo.

If you have a room thermometer, you could adjust the registers, move the thermometer among the rooms, and then readjust the registers until the room temperatures are similar.

@Kiran K Are you certain you are up to the task? If an ordinary supply vent has you bumfuzzled , things you have been asking about are a "tiny"bit more complex.

"Is it just a matter of adjusting the knob pointed by red arrow?"

Unfortunately, to significantly reduce airflow this way usually produces wind noise akin to a jet airplane taking off.

Their are many millions of homes that do not have return ducting from individual rooms. I am retired Navy and lived all over the country and have coincidentally never owned a home with return ducting for each or most rooms.

The home I am in now is a two story, 4 BR, Colonial with a basement. The return plenums are located in the Living Room on ground floor and in the upstairs hall ONLY!.

I have a Heat Pump and also an Oil Burner. Entirely happy.

A transfer grill just opens up airflow from a room without a return to a room / space with a return. In my case, we added a grill in the ceiling of a bedroom to the attic - used flexible duct to another similar grill in the hallway. It created an airflow path that did not require the bedroom door to be open.

"HVAC" stands for Heating, Ventilation, and Air Conditioning. We routinely get evidence that residential HVAC contractors are pretty ignorant when it comes to the "V" part. You can add the above post to that pile.

Residential building codes are driving progressively tighter (i.e., lower natural air infiltration) home construction. While this reduces the amount of energy required for space conditioning, it has the potential to increase the concentration of indoor air pollutants from man-made materials, cooking, moisture, and CO2 levels generated by occupants and their activities. Accordingly, modern codes require some form of mechanical ventilation. The 2021 International Mechanical Code, which forms the core of most state's mechanical codes, dedicates an entire chapter to ventilation. I know you don't do new construction or pull permits, but you might take the time to read it, Ray. It's labelled "Chapter 4 Ventilation." The required ventilation rates are noted in section R403. It requires a minimum ventilation rate of 0.35 air changes per hour, and not less than 15 cfm/person for new residential construction.

Central systems, which rely on an air handler to distribute fresh air, need to deliver fresh air to all living areas. Bedrooms are particularly important given the amount of time people spend in them. If the OP's home even has a fresh air ventilation system, I suspect it won't deliver the required fresh air flow rate to bedrooms which the OP notes have poor air flow even with the doors open.

and CO2 levels generated by occupants and their activities.

So much for Carbon Neutral huh? (Eventually the truth comes out about the carbon neutral scam... it's tied to your ability to breathe or not.)

@klem1 I am upto the task!

1. @Kiran K , I applaud your ability to learn then put to use in 10 days what requires average people years including classroom, apprenticing and practical experience. Over the years my employers sent me a few people fresh out of Central America that had never lived within conditioned space, much less install,maintain and repair equipment. To their credit most figured out the damper leaver on supply vents just by applying common sense but even those were not close to setting up ductwork after being on the job for 3 years unless they took college level engineering classes. In the real world hvac contractors pay engineers to design ducts on paper in situations where it must be right. People come here and elsewhere every day looking for answers because hvac systems in new homes were botched. That fact alone tells us ductwork requires more than a google search. So once again, my hat's off to you in recognition of your uncanny ability to go from first rodeo with a generic supply vent to being up to the task of revamping ventilation in your home.