Chase construction and fireplace bump outs

[elkimmeg]

There has been a lot of discussion about chase and fire place bump out construction. Here is the best description I have found.

CONSTRUCTING A CHASE

Construction of the chase may vary with the type of build-
ing. These instructions are not substitutes for the require-
ments of local building codes. Local building codes MUST
be checked.
Chases should be constructed in the manner of all outside
walls of the home to prevent cold air drafting problems. The
chase should not break the outside building envelope in any
manner.
Walls, ceiling, base plate and cantilever floor of the chase
should be insulated. Vapor and air infiltration barriers should
be installed in the chase as per regional codes for the rest of
the home. Additionally,, that the inside surfaces be sheet rocked and taped
(or the use of an equivalent method) for maximum air tight-
ness.
To further prevent drafts gas line holes and other openings
should be caulked with high temp caulk or stuffed with un-
faced insulation. If the appliance is being installed on a ce-
ment slab, we recommend that a layer of plywood be placed
underneath to prevent conducting cold up into the room.
specifications in manual.
• Locate and install appliance to all
clearance specifications in manual.

 

[DiscoInferno]

Sound like good guidelines, but how many chases out there actually look anything like that description? I have two, one built in 1982 that is just plywood and siding completely outside the insulation envelope and one built in 2003 that I strongly suspect is the same. (Came with modular home, I haven't been inside that chase but the fireplace leaks a lot of cold air.)

 

[G-rott]

Oh the wonders of modular construction. :red:

Garett

 

[DiscoInferno]

Oh the wonders of modular construction. :red:

Garett

It's nothing specific to modular homes, AFAIK. The fireplace and chase are really the exception, otherwise the house is quite tight and well-insulated. (As required by MI code.) It's certainly higher quality than our site-built home in MD. At the time we were drawing up the plans with the company we didn't really know what to demand wrt the fireplace. So we got the default cheapo chase and a non-epa prefab fireplace I'll have to replace some day. We certainly could have had them do otherwise, as we customized most of the house plan. In any case it drafts fine and leaves zero creosote.

 

[jtp10181]

Elk did you copy that from a HHT manual? Or did HHT steal it from a code book?

Thats very well put BTW. Thats basically what we do for the builder now, and charge for it. We got sick of customers blaming the fireplace for the cold air leaks.

 

[keyman512us]

Oh the wonders of modular construction. :red:

Garett

OHH YEAH! Slam the front door and the ceiling lights stop working.... :ahhh: yeah modulars are "Fine examples of quality craftsmanship". hh:

But hey... :coolsmirk: They are great for a few 'service calls' here and there. :zip:

:shut: Inspected??? :sick:

"Hey Jimmy What state is this one going to??? Great...Give me the rubber stamp for that state so I can put the "APPROVED" mark on the kitchen cabinet door". :snake:

Yeah...Makes me want to buy a modular... (looking at the computer screen like I just saw a ghost). :bug:

:-/ "Yes sir...We connected it...You get the standard modular warranty...'Twenty Minutes or Tailights' whichever comes first...Damn it Joey I told you not to slam the front door again...we gotta get outta here sometime today...CAA MAYN" :vampire:

 

[DiscoInferno]

You all do know the difference between "modular" (traditional stick-built in sections in a huge factory) and "manufactured" (mobile home, i.e. double-wide), right?

 

[keyman512us]

You all do know the difference between "modular" (traditional stick-built in sections in a huge factory) and "manufactured" (mobile home, i.e. double-wide), right?

:lol: "Ohh There's a difference??" %-P

By all means...Please "Enlighten me".

"There ain't nuthin' 'Traditional' about building a house in a factory." :ahhh:

While "The Industry" puts out some good press...From my point of view there isn't much difference.

Aside from the "trailers" (which always have the fuse box in the back bedroom closet...behind the water heater...I'de really like to choke the bastard that came up with that bright idea...two code violations right off the bat) :coolhmm:

I cringe everytime I hear "modular/manufactured home"...always a nightmare and good for a laugh. Back in the days (when I used to 'wire' them...together) I loved listening to the "Button Up Crew" trying to mickey mouse s^it togehter...hearing piece after piece of the plumbing system hit the floor while the plumber is basically re-plumbing the place and using "rather colorfull english"...and I'm thinking to myself:

This reminds me of a bad three stooges flick...

Get it done...Get the h^ll out and keep your fingers crossed that the check don't bounce.

I always had fun trying to explain things to "The New Homeowner" and finally began to put it like this: "Sir/Mam...Your house was built (and more importantly wired) by a kid last week whose career started the month before that...at BURGER KING...How can you expect ME to guarantee THEIR WORK???" :grrr:

 

[webbie]

A good chase article would be great for the wiki. I guess I'm a bit confused about this part -

If a house already has an insulated outside wall, then does the chase only have to be insulated up to a certain height? I'm assuming that it contains a "ceiling" at the first floor ceiling level. In other words, it does not make sense to me why you would need two insulated envelopes.

Also, geography and particular appliances have a lot to do with the satisfaction factor.....air cooled chimneys dump LOTS of cold air on the metal prefab fireboxes - does not matter how well the chase is insulated, you end up with the metal fireplace being 20 degrees!

This may not matter in South Carolina, but in New England it's a killer - even in NJ it was! I think builders were happy when most folks started installing gas DV fireplaces, because at least they usually have a pilot and less cold air dumping out. "Cold chases" were a BIG call back reason.

 

[jtp10181]

Typically if you have a chase on an outside wall of the house, a bump out, this is what we would recommend. Treat the walls of the chase on the main floor as an outside wall of the house. 2x6 walls, sheeting, insulation, poly, drywall. Tape or caulk the seams. At the ceiling height (or at 10ft, whichever comes first) build a draft stop and insulate that like an attic (R38 I think... or something). Where this cavity is, DON'T insulate the wall of the room, just hang drywall. This helps the chase area remain part of the room and breathe with the house. This makes the chase are part of the envelope of the room it is attached to. Above that it is recommended to insulate the chase to keep it warm. If you don't want to then ignore the chase and insulate and seal the rooms walls as normal.

If you do not insulate the chase area around the fireplace, you essentially have your fireplace outside, with some rain protection. Fireplaces don't make good windows, no matter what kind they are. Trust me, direct vent gas fireplaces don't make good windows either. We tore apart countless walls (from the outside) to repair bad or lacking insulation jobs due to cold air complaints last winter. I hope to have substantially decreased this for this winter through employee and builder training. After the installers tear into a wall to fix it they remember what was screwed up on the next job they are insulating.

About the air cooled chimneys, we combat this with a "CAK" (Chimney Air Kit). It a metal housing that goes over the giant holes at the bottom of the air cooled section and is ducted to the outside. Its sealed up with hi-temp red silicone. This keeps the cold outside cooling air... outside.

We have pretty much mastered this art at our store through customer feedback and customer complaint.

 

[webbie]

That sounds right, jt.

You are constructing a full house envelope to enclose the fireplace. Therefore, you are effective installing the fireplace inside the home. The upper part of the chase is an attic.

Two enclosed pics from manuals - Lennox and Vermont Castings.

Amazingly enough, they both state that insulation is optional, but highly recommended. I would dispute that, although I know these are installed wrong (without insulation) way down south.