Direct Vent Fireplace Chase Draft Stop Clearance

[MikeBt]

​

I have a Superior DR500-CMP direct vent fireplace that sits inside a chase/doghouse with a rear horizontal vent. There has been a strong draft coming from the fireplace since I purchased the home. I removed the fireplace to determine the issue and found the unit was poorly insulated. I re-insulated with roxul and drywalled the back and sides of the chase, and sealed where the vent pipe passes through the firestop.

I would like to place a draft stop towards the top of the doghouse by horizontally suspending a piece of drywall on a 2x4 frame, and placing insulation above the piece of drywall, basically creating a ceiling in the doghouse. This would create a complete air barrier in the doghouse, effectively cutting off any wind entering through the soffit.

My concern is that the installation manual calls for 64" between the bottom of the unit and ceiling. The manual does not specify whether it is the room ceiling, the doghouse ceiling , or both. Can anyone answer this?

The highest I can place the "ceiling" in the doghouse is at 61 inches due to the slanted peak of the doghouse only being at 66 inches? Is this a safety concern? Is the draft stop I'm trying to create in the doghouse considered a ceiling which doesn't meet the manufacturers spec of 64"?

Thanks for your help.

 

[DAKSY]

Based on the install manual (see attached), I believe you can safely build your shelf at 53" from the floor. When I installed Heat & Glo & Regency DV units with horizontal rear venting configurations, we cleared the top stand offs by 1" with our 2x4 deck. We also sealed EVERY seam in the sheet rock with either aluminum tape or acoustic caulk. As an added seal, we also sealed the entire rear and sides of the meatal firebox with aluminum tape, including the gas line, electrical & thermostat wiring holes...

 

[MikeBt]

Based on the install manual (see attached), I believe you can safely build your shelf at 53" from the floor. When I installed Heat & Glo & Regency DV units with horizontal rear venting configurations, we cleared the top stand offs by 1" with our 2x4 deck. We also sealed EVERY seam in the sheet rock with either aluminum tape or acoustic caulk. As an added seal, we also sealed the entire rear and sides of the meatal firebox with aluminum tape, including the gas line, electrical & thermostat wiring holes...

View attachment 300334

Based on the install manual (see attached), I believe you can safely build your shelf at 53" from the floor. When I installed Heat & Glo & Regency DV units with horizontal rear venting configurations, we cleared the top stand offs by 1" with our 2x4 deck. We also sealed EVERY seam in the sheet rock with either aluminum tape or acoustic caulk. As an added seal, we also sealed the entire rear and sides of the meatal firebox with aluminum tape, including the gas line, electrical & thermostat wiring holes...

View attachment 300334

Based on the install manual (see attached), I believe you can safely build your shelf at 53" from the floor. When I installed Heat & Glo & Regency DV units with horizontal rear venting configurations, we cleared the top stand offs by 1" with our 2x4 deck. We also sealed EVERY seam in the sheet rock with either aluminum tape or acoustic caulk. As an added seal, we also sealed the entire rear and sides of the meatal firebox with aluminum tape, including the gas line, electrical & thermostat wiring holes...

View attachment 300334

Thank you for the reply Daksy. I’ve found your previous posts very helpful and sealed everything with caulk and aluminum tape following the guidance in your previous posts. Is the 53” you mention from the shelf height in your screenshot. If yes, I think the shelf is actually at 35” (I found that when I viewed the manual from a web browser it reversed the numbers, but corrected them when I downloaded the pdf, so 53 becomes 35). The “ceiling” I want to build is about 22” above the standoffs at the top of the unit. Towards the bottom of my screenshot is where it mentions the 64” to the ceiling. I’m confused because how is it permissible to enclose the unit with a 35” shelf, but I need to go up to 64” when building the “ceiling”?

 

[Lennox65]

Thank you for the reply Daksy. I’ve found your previous posts very helpful and sealed everything with caulk and aluminum tape following the guidance in your previous posts. Is the 53” you mention from the shelf height in your screenshot. If yes, I think the shelf is actually at 35” (I found that when I viewed the manual from a web browser it reversed the numbers, but corrected them when I downloaded the pdf, so 53 becomes 35). The “ceiling” I want to build is about 22” above the standoffs at the top of the unit. Towards the bottom of my screenshot is where it mentions the 64” to the ceiling. I’m confused because how is it permissible to enclose the unit with a 35” shelf, but I need to go up to 64” when building the “ceiling”?

View attachment 300342

The 64" clearance to ceiling is the measurement on the finished wall on the face of the fireplace.
That 35 1/4" measurement is the one that applies to what you are trying to do inside the chase.