Cooktop ventilation: Vented or recirculation range hoods and downdrafts
|Dacor Epicure 36" Downdraft Range Hood|
The next challenge we needed to overcome was cooktop ventilation. Vented range hoods were out of the question for the same reason that vented dryers are not appropriate for passivhaus construction. Some range hoods have 1500cfm blowers. That is nearly EIGHT times the air leakage capacity of our extremely airtight house! In fact, even with makeup air provided by our ERVs, that blower unit simply would be strained and incapable of venting anything near that rate.
This left us little choice but to use a recirculating range hood or downdraft unit.
Our kitchen, dinette and great room are essentially all interconnected as we have a very open floor plan. We didn't want a large range hood permanently overhanging our center island as we felt that it would make the kitchen more confining. Miele makes a number of very contemporary European range hoods and one that even retracts itself electronically.
In the end, we opted for a stealth mounted self-retracting downdraft ventilating unit. Downdrafts are not as efficient in ventilating cooktop odors as their ceiling mount equivalents. It is recommended that downdrafts be operated for several minutes prior to actually cooking as to establish a horizontal airflow pattern.
The higher in elevation a fully extended downdraft unit is, the better it will be at ventilating. There were several candidates that we considered. Thermador has a downdraft that raises to nearly 13 inches, which is pretty high, however we couldn't use it because its depth was too bulky to be mounted behind our cabinet draws.
Only one downdraft we found could fit the bill. That was a Dacor unit. What is especially impressive about the Dacor downdraft hood, was when fully extended it reaches 15" in height.
The downdraft hood is also pretty quite during operation as the blower is located a fair distance away in our downstairs basement.
We selected a remote 600cfm blower that was located in our basement in close proximity to our mechanical room. In that area we have an MVHR/ERV/HRV return which can be remotely operated in boost mode. Ventilation challenges were also a reason as to why we selected an induction cooktop. We didn't have to worry about ventilation the byproducts of fuel combustion, namely CO and moisture.
The kitchen has two returns as well. We find this configuration to be effective at ventilating our cooktop without compromising airtightness.
In future postings I will include pictures and videos of the actual interior spaces of our home.