Hvac dont close that door

[paulmars]

Hi, universal advice is to not close door to save energy with a ducked whole house hvac.

I need a new system now and am doing research. I've come to disbelieve that advice. After all let's say i added a room to my home but didn't duck it and kept the door closed. Would my hvac system become unbalanced, have pressure differentials, and work harder? No, I dont think it would even know about that room.

I know technically if the door didnt completely seal air tight, it might be like leaving a window open 1\8". I consider that negligible.

Im also considering the size of the hvac unit. There is a range of sq ft house size for each ton of cooling\heating and if my home had a system larger then it needed, that would be inefficient & closing a door would compound that. However, if my unit was too small for my home, then closing a door (& maybe its duck too) would actually make my system work better. Now of course I expect the reply to be that advice on not closing door is based on house having proper size unit. However, there is a range of house sizes for each ton of heating\cooling recommended.

When I had my current unit installed in 2001 I mentioned that we might be converting garage to a room & then might want a duct added. 3 contractors said we need a two ton unit either way. 4th contractor said a 2 ton would work, but so would a 2.5 & he suggested that since we might be ducking the garage on a later date to go with 2.5. which he stressed would be fine if we never did the garage.

This is of course for a house with a single return that is not in a room being closed.

1952 house that had hvac system added. Return is at one end of house even though there is a closet in the center of house. Also the return is undersize according to the manufacturer's specs. Still, it's worked fine for 23 years.

Your thoughts?

Paul
.

 

[LXCam]

Thoughts?

It’s spelled duct.

 

[Wrench97]

If the rooms have no returns you'll want to leave the doors open, if they have balanced returns/vents in every room it won't matter.
The add on room with no ducts will be uncomfortable at least 2 seasons of the year regardless of the door position depending on your climate of course.

 

[bonneyman]

Thoughts?

It’s spelled duct.

Ah, it's a mute point.

 

[PCustoms]

Ah, it's a mute point.

A mute duck?

 

[bonneyman]

A mute duck?

No, just stealthy!

 

[ratflinger]

What if it's a stink duck?

 

[bonneyman]

What if it's a stink duck?

That's what duck tape is for. It's good for sealing quacks.

 

[isb cornbinder]

Ah, it's a mute point.

Someone was "quacking a joke!"

 

[fitter30]

Heat flows to cold
High RH flows to low
Insulation just slows the flow
Have 4' of insulation at 2' it would be half. 70° 80° 60°

 

[PopcornSutton]

When I moved in my house, I installed a central HVAC (heat pump) including the ducts. I installed one main return duct. I undercut every interior door 3/4".

 

[75gmck25]

One of the issues I've seen with 40's and 50's vintage homes is that they originally had doors undercut to allow for hardwood floors. Later on it became popular to carpet the bedrooms, and the higher pile carpets (maybe even ****!) block off most of the return air. This may cut down the return air a lot when there is no return in each bedroom.

I owned a house in San Antonio that had two large return ducts in the main area, and returns in each of four bedrooms. Temperature was well balanced for both heat and cold. YMMV

 

[aka Larry]

There are so many beliefs/myths on this out there who knows what to believe.

I remember when we first got our house 14 years ago, the party line was to leave the t-stat on one temp to save money. Fast forward 5 years to when I got a programmable t-stat and I found out that line was B.S. I have absolutely saved money on my utility bill since I started using a programmable t-stat.

We have two bedrooms that only get used a couple of weeks out of the year. I keep the vents and doors closed in both of these rooms. IDK if this a good or bad idea, but I can't see the need to heat/cool two rooms with zero usage. I'm sure someone here will tell me I'm wrong though.

 

[Miss the Pontiacs]

 

[dcg9381]

1952 house that had hvac system added. Return is at one end of house even though there is a closet in the center of house. Also the return is undersize according to the manufacturer's specs. Still, it's worked fine for 23 years.

Your thoughts?

Undersized return = not done right. Might impact cooling capacity.
When I built this house, I intentionally instructed the HVAC guys to add oversize returns and specified where they go. Not because I'm some great HVAC genius, but because small returns tend to create substantial air flow noise and also create balance issues in heating and cooling. And around here the HVAC guys just cobble stuff together at whatever the bid price is.

Part of the "issue" and why there is no universal answer is that it depends on your home. My guess is a house built in 1950 has smaller rooms and heating/cooling may be more dependent upon doors being open. Modern homes tend to be larger common spaces and higher ceilings...

 

[bonneyman]

Now that's what they mean by "flex duck"!

 

[Wrench97]

Undersized return = not done right. Might impact cooling capacity.
When I built this house, I intentionally instructed the HVAC guys to add oversize returns and specified where they go. Not because I'm some great HVAC genius, but because small returns tend to create substantial air flow noise and also create balance issues in heating and cooling. And around here the HVAC guys just cobble stuff together at whatever the bid price is.

Part of the "issue" and why there is no universal answer is that it depends on your home. My guess is a house built in 1950 has smaller rooms and heating/cooling may be more dependent upon doors being open. Modern homes tend to be larger common spaces and higher ceilings...

Built in the 50's isn't too far removed from having a vent in the floor of the hallway on both stories for the heat to rise up and heat the rooms from the basement......

 

[Miss the Pontiacs]

Found another one.

 

[larry_g]

In my cheap *** house they put louvers in some of the inside doors to facilitate cold air return.

Google Search

www.google.com

 

[PCustoms]

In my cheap *** house they put louvers in some of the inside doors to facilitate cold air return.

Google Search

www.google.com

I never had a return.

Door to basement had louvers, IIRC there was also some in the panelling of the stairwell/utility room wall. Utility room wall was also vented to garage.