Info on hoods and ventilation systems if interested

Ventilation is a critical element in the equipping of a pizza shop.

By national building code any cooking devise that can raise the temperature of product to 220 degrees is required to have a hood, be it gas or electrically heated. The object of hoods is to exhaust heat and cooking orders whatever the source of the heat.

Health and building departments have stringent rules as to the amount of air to be exhausted by various styles of hoods. It is also a requirement that the same amount of air exhausted from the building be brought back into the building at or near room temperature. The comfort level for workers and customers is also a factor for consideration.

The air that is brought back into the building is referred to as make up air. A properly ventilated building has slightly higher air pressure than outside air pressure. If outside air pressure is higher than inside doors are hard to open and when doors are opened outside air rushes in bringing dust, dirt, humidity,plus hot and or cold outside air in maks uncomfortable drafts. Gas fired appliances also can starve for oxygen and not operate properly. Cooking odors are retained in the building and other problems arise.

Recall the old description of many restaurants as greasy spoons? That was because without proper ventilation everything in the building felt greasy.

There are hoods that have been tested by Underwriter laboratories or others such as ETL. Hoods thus tested and certified require substantially less exhaust and make up air than unlisted hoods some times half as much. Less air exhausted = less A/C lost.

The required make up air can be provided in two ways. A separate make up air unit can be installed or sufficient air conditioning can be provided through the Heating & cooling system to supply the required make up air.

We prefer the use of listed hoods that extract little air from the building plus sufficient air conditioning, which is not great when these type hoods are used.

Initial cost of the listed hoods and sufficient air conditioning is about the same, or a little bit more, as the unlisted hoods and make up air systems .

There is a much better comfort level working with sufficient air conditioning and substantially less cost to operate each year. Rule of the thumb for make up air operating cost is $1.50 per CFM per year,for example, 2000 CFM = $3000.00 yr.

It should be noted that most buildings used for carry out-delivery pizza shops are about 20 ft wide 60 or 70 ft. long and are usually equipped, as an empty building, with a 5 -ton air conditioner. Those first five tons of air conditioning are just about enough to break even with the heat of the oven, heat from the various compressors and food warmers. It is what ever you add to those first five tons of air conditioning that cools your lobby and work area.

Usually we find that 10 to 12 tons or better of air conditioning is required to cool the average shop to tolerable working temperatures. Naturally larger sit down shops need More A/C.

In a few parts of the nation, where the temperature never falls very low and humidity is extremely low a simple filtered fan system that brings in outside air can be used. Unfortunately that type system brings in a lot of extremely hot air during the warmer part of the day and the air conditioning system cannot cope making the shop very uncomfortable to work in.

Most all makeup air system do not cool summer air, they just warm winter air, making the shop extremely hot in summer when super heated air off the roof is brought into the building.

In the very few, always warn and very dry, low humidity areas an evaporative cooler might be used. We do not recommend the athose types of make up air systems.

Hope this helps someone

George mills

I have been fighting with the HVAC company that installed my system from the day I opened. Their solution to the problem of it being too hot in the kitchen was to install a bigger fan to take more air out of the kitchen. Of course this has caused a negative air pressure in the building and like you said causes nasty drafts ( at -40 it is not pleasant to stand in the cashiers place).

Can you recommend a Canadian supplier that would have what I need or even plans to build what I need?

Unfortunately not every HVAC company is competent to do food service ventilation. It is very different than doing the heating and cooling for the average building.

We usually design and supply the ventilation components then have a local HVAC company install and furnish the duct work.

One of the bugaboos of food service ventilation is that a system can qualify under building codes but still produce an uncomfortably warm environment.Your original instillation may have been up to code but obviously not up to the standards of comfort you desired.

Generally speaking the situation you have would never pass a competent building inspectors check out if you were here in the states.

If you can give me some details of your installation I will try to give you a solution to your problem.

What are the dimensions of your building? If you have seating how many?
What is the length and depth of your hood? Does your hood have side curtains at the ends? Those are usually stainless steel panels closing off a portion of the ends.
What equipment do you have under the hood? What is the cubic feet per minute of air you are exhausting not including the fan added later. How are you replacing the exhausted air. Do you have a make up air system? Is the make up air heated in the cool months? Is the MUA cooled in the summer?

George Mills

Thanks for the info George; very interesting

My “Hood” is basicaly a stainless steel box 60" x 96" x 18" with a vent pipe going through the roof to a big fan on the roof. There are no baffles or panels of any sort in the box. There is a makeup air unit that brings outside air into the other side of the 20’ x 24’ kitchen through regular office style ceiling vents. The makeup air can be heated but there is no A/C for it.

If you would like I can send photos of this messed up system.

Just want to put in a quick thumbs up for George for any new TT members. The man knows his business, has some great hood designs, and along with his son is very helpful to the independent pizza operator.

Hi Daddio:

You have some basic problems:

You have a hood that is going to take to much air out of your building.

Your make up air unit is dumping very hot air off your roof into your building

Adding the additional fan only adds to your problems as it is pulling more of your A/C out of the building in addition to the amount going out the hood.

There is no simple solution to your problem.

You should replace you Hood with a certified hood. We would have supplied one that would only extract about 1600 to 1800 CFM. You are probably pulling out up to 3600 CFM. We would have a fan bringing untempered outside air back into the hood by way of a hollow wall panel across the back of the hood which air is then directed up around the equipment and out the hood without entering the room.

We would have extract only about 700 CFM of air from your building and out through the hood. No make up air unit would be required.

Depending on if you building has a properly sized A/C you should be reasonably comfortable all year.

Calculate the required A/C for your size building, include calculations for the number of occupants then add 5 ton to compensate for the ovens and other heat producing equipment.

You must consider that there is radiant heat that comes off the equipment so workers will always be warmer than those not close to the heat producing units.

George Mills

Since I have been fighting this battle from the day I opened would you think it in order to go after the engineer that designed the system and the HVAC company that installed the system to make it right? Should I go after the general contractor that hired these people or just pass it off as fools tax and put in the proper system?

Hi daddio;

I do not consider myself qualified to give legal advise.

Here in the US you can hire a lawyer on contingency and he basically works for a share of the settlement.

In Canada that may be different. I would check with a lawyer and get a professional opinion.

George Mills

Hi Daddio:

I want to reiterate what I said in an earlier posting.your system, as originally installed, may have qualified under the code in your jurisdiction. Your system may be designed to remove the correct amount of air for your hood and to supply the correct amount of make up air.The fact that you are getting hot make up air during the warmer season is probably not be a violation of the code.

The code in the US does not require cooling of make up air and most outfits selling hoods do not let the buyer know that the make up air unit will bring in hot air in the warmer months.That is a short coming on the part of the hood seller but not a violation of the code.

I think some hood sellers may figure that when the buyer starts roasting in the summer they can come back and sell them a large additional A/C unit. Unfortunately the buyer is then paying the operating cost of a make up air unit and additional A/C cost to offset the heat coming in from that unit.

George Mills

Can you direct me to technical specs on the type of hood you are describing? The first thing I will try is to work with the contractor to get things done right. I would like to keep things on a friendly basis.

Send me your Email address and I will send you specs on our system.

George Mills

are captive air hoods worth the money?

This is good info that should be included in the equipment section of the FAQs.

That is a fine product but They make many variations of hoods. It depends on who ever is designing the project using the proper combination of units and components. Bad installations can be made with good equipment.

A lot depends on if the specifier is only interested in making money or if doing the best for the client is most important.

We sell a line of hoods and ventilation products that are as good as C. A. and much better than most.

If you would like us to review your project we will do so at no charge to you.

George Mills