Balancing temperature between two floors

[Hinrix6]

The company that I work for has a two-level office. The furnace is installed on the second floor and uses the plenum between the upper level floor and lower level drop ceiling as the air return. There are two 2x2 egg crate tiles and one 2x4 egg crate tile to facilitate air return. The problem is that it is that when the furnace runs it gets very hot upstairs, and remains cold downstairs. We have several supplies to the lower level, and dampen the upstairs supply, but it doesn't help much. It seems that zoning would be the best option, but we want to try a lower cost alternative if anyone has some ideas.
Two things that stand out to me are:
1. There is an open stairway that would allow hot air to travel upstairs.
2. The returns are at the ceiling, so the hot air gets recirculated.
Any suggestions you have for me are appreciated.

 

[rlitman]

It seems that you've got more bathroom space than office space. Um, is this a brewery, or a meeting house for people with IBS...?

Ok, more seriously, that layout makes no sense to me.
Are the walls open at the top so air can flow over them in the plenum downstairs?
Are there heat registers in the bathrooms (because if not, you need some other heat source in there)?
I'd expect the return to be in the hallway. If you put it near the bottom of the stairs, it could help push air DOWN instead of allowing heat to rise. Then you open the heat registers in the offices, and they should get sufficient heat if the doors are open (or put some sort of opening in the doors).

 

[gregtwojeeps]

Wow, what a HVAC design mess. I have had to maintain MOB's designed that way and what a PIA they were. You need some re-ducting work done IMO Good luck !

 

[DEnd]

Fist thing is make sure all the ducts are hooked up and not blocked.

No install, higher operating cost option, may not work well: Run the HVAC fan continuously
Low install, high operating cost option: install some baseboard heaters

The best option is to get an energy auditor in there and actually figure out what the real issues are. My bet is the HVAC is not well designed for your usage, and you have substantial air leakage so the stack effect is driving hot air out of the upper story and pulling in cold air at the lower story. Fixing those two issues are the only way to decrease your operating cost. Fixing those issues may also present the opportunity to install more insulation, which will further reduce your HVAC operating cost.

Secondly I'd be willing to bet that your HVAC is not supplying you with the correct amount of fresh air per person for the office environment. Meeting ASHRAE guidelines on fresh air has been proven to reduce employee sick days and may also improve employee performance.

 

[zmaxmotorsports]

Shut all of the top floor vents and let the heat gravity feed up the stairways,fine tune it from there by adjusting vents.

 

[Hinrix6]

Thanks for the replies. To answer some questions, the walls are not open at the top, there is foam blocking filling up the bays at the top of the walls. There are not heat registers or returns in the hall bathrooms or hallway. There are registers in the warehouse bathrooms (left side in the drawing) and the private office bathroom at the top of the drawing.
I had a HVAC company come in last winter and they reworked some of the ductwork. Basically they added registers in the lower level. I updated the drawing to show where the registers are located (green circles). The company nearly doubled the number of registers on the fist level, and they added egg crate tile to the office shown in the lower left corner of the drawing. Each floor is a little under 1,800 square feet, so we are not talking about a huge area. The HVAC company is now pushing zoning, that is why I wanted some input from GJ members. I am embarrassed to say that I hadn't thought about the top of the walls being blocked. Thank you rlitman for pointing that out.
We also have the system set to circulate, so the fan runs pretty often, but it doesn't seem to help balance the temperature between floors.

 

[nadogail]

As a suggestion for a "cheap fix".

Install a vertical tube from the hot area to the cool area immediately below it, then add a "Muffin Fan" to move the warm air to where it's wanted.

Muffin Fans work fine, last a long time, and can be had cheaply.

 

[Jackfre]

You might try Tjernlund's Airshares. I used thousands of these in different projects and they work well.
http://www.tjernlund.com/airshare_ventilation.htm

 

[gregtwojeeps]

A novel follows.....

Has the HVAC company performed a thermal air balance on every supply register on the whole system, to find out each registers CFM supply output ? Until they know the CFM output on each supply register, they are rolling dice in getting the proper air flow balance. I am not seeing any return air system(s) on the second floor. Do they exist or not ?...

The whole system if drawn in these posts correctly, is problematic because of the way the return air system is set up. I am only seeing "above ceiling plenum return" egg crate return ceiling grills... in just two rooms..... So the furnace is trying to blow "air in to a sealed box" whenever it has a supply register in a room that has no way for that supply air ...to be pulled back in to the return air systems.

These two "return egg crated" rooms have the potential of the room's door's being closed, so the possibility exists that at any time.... the rooms doors are closed, the WHOLE return air of the system will just be furnished from these room's egg crate RA grills...

The supply air total CFM discharge output is in direct relationship to the amount of return air the furnace blower can pull in. The blower cannot blow more air out of the supply plenum, than it is receiving in its return air plenum.
( this is why filters need to stay in good order) ...

We know that warm air rises. So yes, every heating season it may help throttling down the registers on the second floor to force more heated air to the lower floor. But then, on unseasonably warm days and when its time to change from the heat to the cooling season...someone has to play the register adjusting game. If duct booster fans are used, then when they fail, someone has to hunt them down...because guaranteed the original installer of the fan will not be around when they go bad. It is always best to make the syatem operate as it should be designed to, without gadgets, add ons and such.. .

Just my opinion ...but whomever owns this facility would be well justified in hiring the services of a mechanical engineer to do a thorough survey on the HVAC design of the building. It appears to me at least, the HVAC "parts" cannon is now being fired in the building. ....

As mentioned above, many offices have "sick" air. Not meaning to take away from any HVAC contractors expertise, but I have seen way too many prominently residential grade HVAC installers, put in some random commercial jobs. They are in the same field, but the two installation fields differ a lot at times . ...

Because the commercial building type of construction, floor design, and occupant use... all make the duct/air handling capabilities of commercial buildings .....require different designs of those that work in residential buildings. Commercial HVAC is designed to be suited for the building's use, so the system will be efficient,comfortable and easily maintained to keep employees and heat producing office equipment running well.
All JMO

 

[Hinrix6]

gregtwojeeps - thanks for the detailed post. I will try to answer you questions. The HVAC company did not perform a thermal air balance evaluation.

I am sorry, but I missed the cold air returns for the second floor. The furnace has an opening on the side, there is a filter installed, and rectangular ductwork with two returns cut in. I know very little about HVAC, but this does not look right to me.

You mention the two egg crated room having the potential of having the doors closed and the whole return air being furnished by these two rooms. The doors to those room are virtually always closed.

The HVAC company that installed this system prides themselves as both residential and commercial, but I am not so sure about the commercial side. I'm not going to start bashing them, but they installed air handlers for the air conditioners in our warehouse and they have been leaking since day one...that's an entirely different problem.

 

[gregtwojeeps]

I'll keep this one short....

For most property owners / landlords it is all about the money. We all know the building should have had a HVAC unit per floor to ever operate as it should..... BUT..... money talks and the owner in my opinion...most likely took the lesser bid of just one unit to do two floors. JMO .

 

[Hinrix6]

I added two 2x2 egg crate ceiling tiles in the hallway and opened some of the styrofoam blocked bays. That's when I realized that the blocking to the east of the hall was actually a joist that runs the length of the wall. It turns out the joists run North-South to the East of the hall and East-West to the West of the hall. Suggestions are welcome!