So I have finished a "Tiny" (small) home build.
The home totals 720sq feet with a720 q ft unfinished basement.
The home is heated by a forced hot air gas furnace. I was forced to install the ductwork in the basement myself. The furnace was vented out side, but the fresh air intake on the top was not vented outside.
When the blower comes on, there is sufficient suction in the basement to pull the basement door (first floor living area) shut.
First off, should the fresh air intake be vented outside ?
Second, what is causing the imbalance and suction from the basement, lack of returns in the living area, lack of supply in the basement ?
Any and all help would be most appreciated.
Thanks,
Brad

Not a professional, but redoing my system soon. From what I was told:

Without returns, you are creating negative pressure in the basement and positive pressure in the living area, just for the interior air.
If you are not pulling in combustible air, but drawing that from the basement area, that negative pressure will increase.

I would create a return system that isolates the conditioned air to the living area. It will increase efficiency by properly moving the heated air through the space, and drawing the cooler air (from doors and windows) away.

As for fresh air intakes, it depends on your house design. A newer tight house will need an air intake, especially if using a high efficiency furnace.
Older homes with enough "leaks" will pull in enough air to offset the loss to the furnace.

Please explain your return air ducting/design, I'm assuming you're pulling return air from the basement?

Any high efficient furnace should be two piped. Not always required, but highly recommended.

quote:

Originally posted by Excam_Man:
Any high efficient furnace should be two piped. Not always required, but highly recommended.

Zero make up air is going to be an issue. For every cubic foot of air that goes out the vent stack, another cubic foot has to either be directed back in or leak back in equalize atmospheric pressure. Plus, if it's leaking in, you have to climate condition that air (either heat it or remove the heat and humidity) to maintain your space temperature inside.

I only have a degree in climate Control Technology (HVAC) but my area of expertise is appliances. But before leaving this to Excam (who is one of our forum HVAC SME's) I'll add that I bet the furnace issue is just the tip of the iceberg in the issues the OP is going to experience.

In the living area I have a 10"x10" return in the bedroom and two 4"x10" supplies. In the Living room/Kitchen, I have a 10"x10" return and three 4"x10" supplies, in addition there is a 4"x10" supply in the bathroom.
In the basement, there is a 4"x10" and a 12"x8" return on the side of the cold air plenum. I have a 6" return ducting from the return line and two 6" supply ducting from the supply line.

quote:

Originally posted by BradleyS:
there is a 4"x10" and a 12"x8" return on the side of the cold air plenum

There's the root cause of the problems.
No returns in kitchens, bathrooms, utility and equipment rooms.

What type of water heater is installed?
As with an atmospheric vented unit, the furnace can pull the combustion gases from the venting. Which is a major safety issue due to carbon monoxide.

Here is an image of the layout of the living area.
https://i.imgur.com/4ze8Uis.jpg

In addition to Excam and Brads advise I would also say your propane fireplace should also have a fresh air supply and is hopefully vented as well unless it’s a direct vent model.

Ventless gas fireplaces are a thing.

Whether or not they're 100% safe or smart can be argued, but they're available and within code.

Maybe within code but I don't believe I'd want an unvented gas fireplace in a 720 sq ft home.
I'll take that back, I don't think I'd run an unvented FP "a lot" in a 720' home.

Have a picture of the equipment room, which includes the furnace?

https://i.imgur.com/joRA33k.jpg

https://i.imgur.com/IRyXI5q.jpg

I apologize for the mess.

The OP states you installed the ductwork... did you have plans to follow?
What about the rest of it?

The returns at the furnace need to disappear.
It looks like the two upstairs returns are connected with 6" piping?
Filter inside the blower door 16x25?
I'd run a second pipe for the combustion and use a concentric kit for the termination.
Ducting should be reduced as it gets further from the furnace, as runs are taken off.

What's the furnace model?
What's the outside measurements of the return/supply ductdoard ducting?

Air conditioning?

Electric water heater, so no CO concerns there.

The Propane fireplace in the living area idea was scrapped.

I have no plans to work from. The electrician began to install the furnace, due to no HVAC specialist in the area willing to do the work. I told the contractor to have the electrician discontinue the furnace install, after he stated that he knew little about gas furnaces. He then got angry and walked off the job and didn't complete the electrical.

Recently I had an HVAC guy, after having the
work order open for two months, come by to advise on balancing the system. He recommended the additional larger return vent on the cold air plenum and attaching the open one (6" flex pipe hanging to the floor)) to a new vent in the living room.

All venting is done with 6" duct pipe.

The filter is a 21"x24"x1"

Furnace is an Airtemp Non-Weathered Model VG7TC-24B1

No air conditioning.

When you say the ducting should be reduced as it gets further from the furnace, is that the size of the duct ?
"the rest of it", are you referring to the two supply ducting and the one returning hanging down to the floor. The HVAC guy told me to run the supply to the floor to better mix the cold and hot air.

Cold air plenum is 18"x22", return run is 12"x16".

Your continued advise is Greatly appreciated.

quote:

Originally posted by RogueJSK:
Ventless gas fireplaces are a thing.

Whether or not they're 100% safe or smart can be argued, but they're available and within code.

Maybe in your neck of the woods but not in mine and either way certainly require an outside air source…

Let's start from the beginning.
Where did the furnace come from and who sized it?

The supply duct size?

quote:

Originally posted by Excam_Man:

quote:

Originally posted by BradleyS:
there is a 4"x10" and a 12"x8" return on the side of the cold air plenum

There's the root cause of the problems.
No returns in kitchens, bathrooms, utility and equipment rooms.

What type of water heater is installed?
As with an atmospheric vented unit, the furnace can pull the combustion gases from the venting. Which is a major safety issue due to carbon monoxide.

I am no expert by any means but I worked for a few years (while layed of from auto industry) for a hvac contractor installing furnaces/ductwork in new homes. He told me to never put returns in from kitchens & bathrooms to prevent oders from being spread throgh the whole house.
Made sense to then and still does.
BradleyS, try covering up part or all of the basement return and see how that works out.
If your stair door closing is your only beef then get a door stop.
I would guess that code requires a oustside air supply for combustion.

quote:

Originally posted by Excam_Man:
Let's start from the beginning.
Where did the furnace come from and who sized it?

The supply duct size?

The Contractor had a rep from R.E. Michael CO. in Cumberland Md come in and size the furnace.

The Fiberboard main supply is 12" x 16"

What happened to said contractor?

This system is messed up from the word go.
60k for 750 sq ft, that thing will never see second stage operation.

Returns at the furnace need to disappear.
Dual pipe with a concentric kit for combustion air and exhaust.
6" return runs are too small.
Not enough return air from upstairs.
Piss poor air filter setup.
Small supply and return main trunks.
Small supply and return duct runs.
Ducting not downsized as runs are pulled from the main trunk.
Major restriction on the supply plenum to duct connection.

I'm sorry to say, I recommend ripping it out and starting from scratch with a proper load calculation.
Then select the properly sized equipment and run the required sheetmetal ducting.

Quote from Excam man: "a proper load calculation.
Then select the properly sized equipment and run the required sheetmetal ducting."

I second this! Sounds like you need a couple more opinions from reputable establishments. Anyone who skips this process must be avoided. The end result will be disappointment and costly.