Put a tenant below your living room and the furnace room stops being a storage closet. It becomes part of the wall that keeps a fire in one unit from reaching the other.
This is where a lot of basement suite permits get tangled: the fire separation looks fine on the architectural drawings, then the ducts and the furnace room punch holes right through it. Here is how the pieces fit.
In a house with two units, the walls and ceiling between them have to slow a fire down long enough for people to get out. The furnace room usually sits right in the middle of that, in the basement, under the main floor.
Ducts, return air paths and the furnace room itself can all break the separation if nobody plans for them. The architectural drawings show the separation. The HVAC design has to respect it.
Converting an older house can sometimes use compliance alternatives for existing buildings. New construction cannot. That is why two suites that look identical can have different requirements.
The suite’s ventilation also goes on the ventilation summary (RMVDS) submitted with the permit.
Normally the furnace room is enclosed as part of the separation. Where that is not practical in an existing house, building departments accept alternatives. Oshawa’s guide, for example, describes a sprinkler head in the furnace room and mineral wool packed into exposed joist spaces above.
Every duct through a rated wall or ceiling has to be detailed on the drawings. Not improvised on site.
No shared return air between units in new construction. A return grille in the suite that pulls air from the main house breaks both the HVAC rules and the separation.
Some older houses use a route where a duct smoke detector shuts the system down. That is a specific design with specific requirements.
Next to each sleeping area, on each storey of the suite, and in bedrooms that share a wall, floor or ceiling with the furnace room or garage.
Interconnected smoke alarms between the units are part of the life safety package. The architectural designer and electrician cover this side.
The trunk line cut through the rated ceiling with nothing done about it.
Pulling air from the suite back to the main furnace. Not allowed in new work.
No separation above the furnace room and no accepted alternative.
Bedrooms next to the furnace room with no alarm.
The cleanest suites usually give the tenant their own heating and ventilation, so no ducts have to cross the separation at all. A ductless heat pump in the suite and a separate HRV is the common answer. See heating options for basement apartments.
Either way, the HVAC design and the architectural design have to agree before the permit goes in. See the legal basement apartment checklist.
Building a basement suite? Send the floor plans. We design the suite HVAC so it works with your fire separation, not against it.
Get Free Quote →The furnace room is part of the fire separation between the units. Where a proper separation can be built around it, that is the normal route. In some existing houses where that is not practical, building departments accept alternatives. Oshawa’s guide, for example, describes a sprinkler head in the furnace room and mineral wool packed into exposed joist spaces above it. Your building department decides what applies to your house.
Where there is a fuel-burning appliance or an attached garage, CO alarms go next to each sleeping area, on each storey of the suite, and in bedrooms that share a wall, floor or ceiling with the furnace room or garage. The 2024 code also added requirements for hardwired alarms.
They can, but each penetration has to be detailed so it does not become a hole in the separation. That is a design job, done on the drawings, not something to figure out with a hole saw on site.
In new construction, return air cannot be shared between units, so in practice no. Some older houses can use an alternative route where a duct smoke detector shuts the system down. See does a basement apartment need its own furnace.
Yes. Houses being converted can sometimes use compliance alternatives for existing buildings that new construction cannot. That is why two suites that look the same can end up with different requirements. Ask early.
The architectural designer handles the fire separations. The HVAC designer has to work with them so ducts, returns and the furnace room do not break what they designed. Both need to be on the same page before the permit goes in.
Send your suite drawings. We do the heat loss and HVAC design for each unit, planned around your fire separation.