Shivering with the thermostat set to 75 F HVAC question

  • Thread starter Moonbear
  • Start date
  • Tags
    Hvac Set
In summary: The cardboard would redirect the airflow so that it blows on the side of the desk away from the person, and not directly on them.
  • #1
Moonbear
Staff Emeritus
Science Advisor
Gold Member
11,923
54
This question occurs to me from time to time, but I never remember to ask it. When HVAC systems are designed, does anyone bother to take into account "wind chill factor?" I've been feeling about ready to freeze to death in my office for quite some time, in spite of the thermostat being set for and the temperature reading about 75 degrees F. However, there was a day earlier this week that the ventillation system had something go wrong and it was shut down in my office for about a day. The temperature dropped down to about 68 F, but I was relieved to finally feel warm in my office. The difference? I didn't have a vent over top of me constantly blowing air at me. I realize that there is a need for a certain amount of air exchange in buildings, but does it make sense for it to be so great that I end up cranking up the thermostat to account for wind chill factor while in an office? (It could just be a really crappy HVAC system...Russ has experienced the wind tunnel when he visited me some time ago and we walked through one corridor that is rather drafty, to put it mildly.)

(On the plus side, the broken lab ventillation system that had the opposite problem of leaving the rooms overheated without enough air flow to remove unhealthy fumes finally got fixed when we threatened to cancel our classes after I got sick from being overheated one day and insisted that the students shouldn't have to spend more time in a lab than I could tolerate.)
 
Engineering news on Phys.org
  • #2
The vent vanes and vent position are sometimes not so great. There are a couple people where I work (in an intelligent building that we design control networks for) who have put their own airflow-modifying pieces of cardboard hung under the ceiling ducts to redirect the airflow. The direct draft airflow is a mistake in office design, and you should request a change if your facilities folks can handle it.

If they can't handle it, have Evo get a ladder and hang a redirector piece of cardboard under the vent. Have your med bag close by, though...
 
  • #3
berkeman said:
The vent vanes and vent position are sometimes not so great. There are a couple people where I work (in an intelligent building that we design control networks for) who have put their own airflow-modifying pieces of cardboard hung under the ceiling ducts to redirect the airflow. The direct draft airflow is a mistake in office design, and you should request a change if your facilities folks can handle it.

If they can't handle it, have Evo get a ladder and hang a redirector piece of cardboard under the vent. Have your med bag close by, though...

I was thinking of stuffing a rag in the vent...at least on the side that directs air toward my desk, and leave the air to flow only toward the wall away from me. I don't need a ladder, I can climb on my desk to reach it. :biggrin: I doubt anyone will change the design of the airflow in my office, since the office is only about a year old as it is. On the plus side, once summer arrives, they did give me a window that opens, so I can just let in warm outside air and let the HVAC work like a nice fan for me. :rolleyes:
 
  • #4
Fair enough. No Evo sub-contractors needed.

Cut a piece of cardboard about the size of the vent, and hang it with 4 pieces of wire under the vent. Does your office ceiling use the traditional hung ceiling, with panels and cross-members? If so, it's easy to put the 4 wire hangers at the 4 corners of the vent.
 
  • #5
Maybe it's just a Canuck thing, but we have floor-register deflectors available in every hardware store. They're just a length-adjustable 90° plastic deflector that redirects the airflow and magnetically attaches to the register. They cost something like $1.50 and last a lifetime.
Hey, Moonie... does this mean that you wore out that nice electric bra that I made for you? :frown:
 
  • #6
berkeman said:
Fair enough. No Evo sub-contractors needed.

Cut a piece of cardboard about the size of the vent, and hang it with 4 pieces of wire under the vent. Does your office ceiling use the traditional hung ceiling, with panels and cross-members? If so, it's easy to put the 4 wire hangers at the 4 corners of the vent.

How would a piece of cardboard under the vent help? It would be like adding another layer of fins to the two or three it already has, but wouldn't the air still blow on me? I'm contemplating stuffing in some HEPA filter, just to reduce the airflow without cutting off my heat entirely. Come summer time, I couldn't care less if I cut off the A/C, I prefer having the windows open anyway.
 
  • #7
Danger said:
Maybe it's just a Canuck thing, but we have floor-register deflectors available in every hardware store. They're just a length-adjustable 90° plastic deflector that redirects the airflow and magnetically attaches to the register. They cost something like $1.50 and last a lifetime.

I've never seen those, but the ceiling vents in a commercial building are completely different shape and sizes from a floor register in a house.
 
  • #8
Moonbear said:
the ceiling vents in a commercial building are completely different shape and sizes from a floor register in a house.

Okay, I wasn't sure what sort of vent you had. Still, the basic principle should apply. Let's say that it's a 1' x 1' vent. Buy a 1' section of 1' diameter ABS or PVC pipe and saw out a 1/4 section of it. Cap off the ends and mount it by whatever means right below the vent. The airflow will be deflected at 90°. It still comes into the room for recycling, but won't directly impinge upon your magnificent personage.
 
Last edited:
  • #9
Moonbear said:
How would a piece of cardboard under the vent help? It would be like adding another layer of fins to the two or three it already has, but wouldn't the air still blow on me? I'm contemplating stuffing in some HEPA filter, just to reduce the airflow without cutting off my heat entirely. Come summer time, I couldn't care less if I cut off the A/C, I prefer having the windows open anyway.

It solves the problem in at least 2 offices that I'm briefed on in our "intelligent" building. Cut the carboard rectangle to match the dimensions of the ceiling vent. Hang the deflector about 6" below the vent. This forces the air streams toward the walls of your office, instead of right down on you. If I'm misunderstanding your office HVAC vent layout, adjust it for your office. Cardboard pieces can be good makeups for incompetent HVAC and Facilities personnel.

Send me pics of your office if you want more cardboard advice...
 
Last edited:
  • #10
Moonbear said:
How would a piece of cardboard under the vent help?

I think berkeman meant the cardboard should be horizontal, to stop the air from blowing directly downward onto you.

EDIT:
I might even make the cardboard a few inches larger than the vent opening.
 
  • #11
berkeman said:
It solves the problem in at least 2 offices that I'm briefed on in our "intelligent" building. Cut the carboard rectangle to match the dimensions of the ceiling vent. Hang the deflector about 6" below the vent. This forces the air streams toward the walls of your office, instead of right down on you. If I'm misunderstanding your office HVAC vent layout, adjust it for your office. Cardboard pieces can be good makeups for incompetent HVAC and Facilities personnel.

Send me pics of your office if you want more cardboard advice...

Sorry, I didn't get back sooner to follow up.
This is the sort of diffuser already on the vent:
http://www.lowes.com/lowes/lkn?action=productDetail&productId=265652-33599-ABCD2X2&lpage=none

It's placed dead center in the room (the office isn't very big) and my desk is pretty much right under it...slightly off to one side.

I haven't had a chance to try the cardboard approach yet. I'm not sure if it'll do much since the office is so small that any airflow is going to chill me. But, when I'm done moving and have lots of extra cardboard around, I'll give it a try. I guess the basic construction of this deflector is cardboard and paperclips? :biggrin:

In the meantime, I've been loving the days they work on the ventillation systems and it's shut down to my office. But, I pick my battles. On the plus side, it does create a positive pressure air flow in my office (very hard to keep my door just a crack open without it blowing closed), which means when the ventillation in the anatomy labs isn't working, I don't get those odors into my office.
 
Last edited by a moderator:
  • #12
Are hanging pieces of cardboard right next to a HVAC vent considered a fire hazard? I think you can get spray-on fire retardant if it were.
 
  • #13
I think HVAC devices tend to be high velocity because customers like to feel them working, it feels more cool, etc. Which is awful for the reason moonbear described. I'd just hang a piece of cardboard like everyone says, with enough gap between it and the ceiling to allow adequete air flow. The gap has 4 sides, so about 1/4 the width of the vent should be plenty. Paper burns at 451 degrees fahrenheit according to a famous book; I doubt it will ever get that hot.

Better yet see if you can get the real diffuser installed, but cardboard should work in the mean time.
 
  • #14
MATLABdude said:
Are hanging pieces of cardboard right next to a HVAC vent considered a fire hazard? I think you can get spray-on fire retardant if it were.

Good question. I don't think so, but I could be wrong. I'm pretty much the safety-dweeb around the office, though, and I don't see anything hazardous about it. Now if it is anywhere near the fire sprinkler heads...
 
  • #15
berkeman said:
Good question. I don't think so, but I could be wrong. I'm pretty much the safety-dweeb around the office, though, and I don't see anything hazardous about it. Now if it is anywhere near the fire sprinkler heads...

Well, that sounds logical. If if its chilling for Moonie when she just sits in a wind, imagine how chilling it will be once she gets sprinkled with water.

I think other piece of cardboard hanging below the sprinkler will do.
 
  • #16
Moonie, you should pop a ceiling tile or two around your duct. Sometimes there is a crude butterfly-type damper in the duct above the diffuser, so the installer can balance the system. There have to be some dampers somewhere in that duct-work. Time for investigation.

EDIT: If you find a damper and can throttle it back, you owe me a jar of that wonderful-looking habanero jelly.
 
  • #17
Sorry I missed this thread before...
Moonbear said:
Sorry, I didn't get back sooner to follow up.
This is the sort of diffuser already on the vent:
http://www.lowes.com/lowes/lkn?action=productDetail&productId=265652-33599-ABCD2X2&lpage=none
Ok, so you have a diffuser as opposed to a grille (just angled slots). That's good, but it sounds like whoever sized it screwed-up. Diffusers are designed to use the coanda effect to make the air stick to the ceiling, spreading out, then falling down along the walls (this is called "dumping"). But the coanda effect requires a certain amount of velocity out the diffuser. Not enough velocity and the air doesn't stick to the ceiling, but instead drops straight down. For relatively small, individual offices, a 12x12 diffuser should be used.

A few quick load questions: are you on an oustside wall? How big is your window? What direction do you face? What are the office dimensions?

One other thing - since in the summer, most of the load is at the window, and you likely have a return by your door, the convection pattern should be from the center, out, but also from the center, toward the outside wall, then back up at the inside wall toward the return. In your case, you might be able to fix your "dumping" problem by using some paper and tape to block 3 of the 4 sides of the diffuser, leaving the side facing the window open. Hopefully, you'll end up with enough velocity that it won't dump on you but instead will stick to the ceiling, travel toward the window, and then fall down along the window, cancelling the heat generated at the window.
 
Last edited by a moderator:
  • #18
russ_watters said:
Sorry I missed this thread before... Ok, so you have a diffuser as opposed to a grille (just angled slots). That's good, but it sounds like whoever sized it screwed-up. Diffusers are designed to use the coanda effect to make the air stick to the ceiling, spreading out, then falling down along the walls (this is called "dumping"). But the coanda effect requires a certain amount of velocity out the diffuser. Not enough velocity and the air doesn't stick to the ceiling, but instead drops straight down. For relatively small, individual offices, a 12x12 diffuser should be used.
I think that is about the size it is. But, yeah, what you describe of the air dropping down is about right...I sit below it and feel a constant draft on me (it doesn't cycle at all, and I don't know if it should, it just blows air all the time unless something is broken).

A few quick load questions: are you on an oustside wall? How big is your window? What direction do you face? What are the office dimensions?
I am on an outside wall. Not quite sure the size of the window, since I haven't measured it, but a guesstimate would be 4ft wide by about 3 ft high (it might be more square, but seems a bit wider than high). The office dimensions are too small. :biggrin: Probably about 10'x10'.

One other thing - since in the summer, most of the load is at the window, and you likely have a return by your door, the convection pattern should be from the center, out, but also from the center, toward the outside wall, then back up at the inside wall toward the return.
Oh, no, I think a return would cost too much. :rofl: I have no return, just air blowing in. Seriously. I'm sure that's why the door blows shut if I try to leave it open a crack. :rolleyes: Hey, you've seen first hand how wonderfully designed the HVAC is around my building. I don't even know this one...do returns actively "suck" air into them, or are they just passive places for air to get out? Maybe that's the entire problem, that the air blowing in really has no place to go, so just swirls around every which way creating turbulence instead of a steady flow. Gotta love government contracts to the lowest bidder. :rolleyes:

In your case, you might be able to fix your "dumping" problem by using some paper and tape to block 3 of the 4 sides of the diffuser, leaving the side facing the window open. Hopefully, you'll end up with enough velocity that it won't dump on you but instead will stick to the ceiling, travel toward the window, and then fall down along the window, cancelling the heat generated at the window.
I sit more toward the window side of the vent, so I think I'd opt to blow it toward the door rather than window...the door is on the wall opposite the window. If that creates the opposite problem of too much heat sneaking in from the window in summer (it does overlook a wonderful roof of a lower level that likely throws off a lot of heat), I can always move the paper to a different side.

I probably just have to wait a year or two, and the system will break like everything else in our building, and then it'll be a year before they fix it, and I'll be warm for a while.
 
  • #19
I should've read all the responses and replied to them all in one post.

berkeman said:
Good question. I don't think so, but I could be wrong. I'm pretty much the safety-dweeb around the office, though, and I don't see anything hazardous about it. Now if it is anywhere near the fire sprinkler heads...
Hmm...I'm not sure about that either. Anything stored within 18 inches of the ceiling is considered a fire hazard, but I'm not sure about just a piece of cardboard dangling from the vents. Russ' suggestion might be more inconspicuous. I can always take it down if they complain during a fire inspection, and put it back after they do the reinspection. :wink: I don't think they look up unless there are shelves, though. Usually they're checking for overloaded outlets, too many wall decorations, and location of fire extinguishers during the safety inspections.

turbo-1 said:
Moonie, you should pop a ceiling tile or two around your duct. Sometimes there is a crude butterfly-type damper in the duct above the diffuser, so the installer can balance the system. There have to be some dampers somewhere in that duct-work. Time for investigation.

EDIT: If you find a damper and can throttle it back, you owe me a jar of that wonderful-looking habanero jelly.

That habanero jelly wasn't mine, I just found a photo online. :tongue: But, I already know the answer to that particular question. The dampers are somewhere else in the ductwork and controlled electronically. I know because the dampers close if the power goes out, such as during a thunderstorm, and it usually takes them a day after reporting the problem to go crawling around somewhere to find the malfunctioning one and reset it (I don't report these things since I prefer having the ventillation off, but the students sharing the windowless office next to mine usually call it in :grumpy:). Maybe that's a safety feature to close off the vents when power is out, except they don't seem to reset properly. I'm sure they are controlled electronically so if there's ever a spill of something hazardous in one of the labs, they can remotely close the vents off without sending maintenance personnel into the spill area since part of the procedure for reporting a spill of anything that can be airborne is to call maintenance and have them shut down ventillation to the area to keep it from contaminating the rest of the building.
 
  • #20
My post contained an error. I had gone back after typing it to add the part in parentheses and added it to the wrong sentence:
russ_watters said:
Diffusers are designed to use the coanda effect to make the air stick to the ceiling, spreading out, then falling down along the walls . But the coanda effect requires a certain amount of velocity out the diffuser. Not enough velocity and the air doesn't stick to the ceiling, but instead drops straight down (this is called "dumping").
Ie, "dumping" = bad.
 
  • #21
Moonbear said:
Oh, no, I think a return would cost too much. :rofl: I have no return, just air blowing in. Seriously. I'm sure that's why the door blows shut if I try to leave it open a crack. :rolleyes:
Yes...
...do returns actively "suck" air into them, or are they just passive places for air to get out? Maybe that's the entire problem, that the air blowing in really has no place to go, so just swirls around every which way creating turbulence instead of a steady flow. Gotta love government contracts to the lowest bidder. :rolleyes:
Well conservation of mass says the air can't just keep flowing in unless you have a balloon for an office, but yeah, returns actively suck the air out.
 
  • #22
Hi Moon,
there should be 2 dampening devices installed on the supply run, one of them will be in the ceiling diffuser itself & the other should be in the branch line near the main supply above the drop ceiling. Try adjusting the damper at the diffuser
 

1. What causes shivering when the thermostat is set to 75 F?

Shivering is a natural response to feeling cold, which is triggered by the body's thermoregulation system. When the thermostat is set to 75 F, the body may still feel cold if the environment is not at that temperature.

2. Can shivering be a sign of a malfunctioning HVAC system?

Yes, shivering can be a sign of a malfunctioning HVAC system. If the thermostat is set to 75 F but the room still feels cold, it could be due to a malfunctioning heater or a problem with the thermostat itself.

3. How can I prevent shivering with the thermostat set to 75 F?

To prevent shivering with the thermostat set to 75 F, you can try adjusting the thermostat to a higher temperature or using additional heating methods like a space heater. It is also important to ensure that your HVAC system is properly maintained and functioning correctly.

4. Why do I still feel cold even though the thermostat is set to 75 F?

There are several reasons why you may still feel cold even with the thermostat set to 75 F. It could be due to poor insulation in your home, drafts, or a malfunctioning HVAC system. It is best to troubleshoot the issue to determine the cause.

5. Is shivering with the thermostat set to 75 F bad for my health?

Shivering can be uncomfortable, but it is not necessarily bad for your health. However, if you are constantly shivering due to a malfunctioning HVAC system, it could lead to discomfort and potential health issues. It is important to address any issues with your HVAC system to maintain a comfortable and healthy environment.

Similar threads

Replies
4
Views
1K
  • Mechanical Engineering
Replies
19
Views
2K
  • Electrical Engineering
Replies
11
Views
1K
  • Mechanical Engineering
Replies
3
Views
2K
  • Mechanical Engineering
Replies
2
Views
3K
Replies
10
Views
416
  • Mechanical Engineering
Replies
2
Views
5K
  • Mechanical Engineering
Replies
30
Views
2K
  • Mechanical Engineering
Replies
8
Views
2K
  • Engineering and Comp Sci Homework Help
Replies
7
Views
1K
Back
Top