Heating & Ventilation: Space Heaters, Bathroom Exhaust Fans, and Honeywell Thermostats — a Howden Decision Guide

In January 2025, I had a call from a waste transfer company. They'd searched for commercial waste Howden and landed on a forum full of advice that sounded logical: buy a bigger fan. They did. It still didn't fix the problem.

I'm a senior applications engineer at Howden. I've spent 14 years matching air-moving and heat-exchange equipment to real-world spaces. I've personally made—and documented—22 significant mistakes, totalling roughly £86,000 in wasted budget. This article is the checklist I wish I'd had.

There's no universal answer. There's the right answer for your scenario.

“Which space heater should I buy?” “What size bathroom exhaust fan?” “How do I program my Honeywell thermostat?”

Those are reasonable questions, but they're often the wrong starting point. They leap to a product before asking what the space actually needs.

In 2012, a client asked me to recommend a cheap heater for their sorting shed. I suggested two space heaters and a timer. It worked—for about a month. Then cardboard dust built up around the heating element, the thermal cut-out kept tripping, and the electricity bill went from £260 to £610 in a single quarter. They eventually spent £1,400 on low-temperature radiant heating. The space heaters cost £240. I still remember that £1,160 gap.

So here's how I'd split the decisions. Three scenarios cover most of the calls I get: A, a commercial recycling or waste facility; B, a bathroom that needs a decent exhaust fan; C, a heating system with a thermostat nobody knows how to program. Find your scenario before you buy anything.

Scenario A: You're dealing with a commercial recycling or waste facility

When someone searches for commercial recycling Howden or commercial waste Howden, they usually want a collection service. But if you run the facility that receives the waste, your question is different. You're not asking how to get rid of rubbish. You're asking how to keep a building safe and workable while the rubbish sits inside it.

From the outside, it looks like one big extractor fan is enough. The reality is that a waste shed needs balanced supply and extract airflow, sometimes with filtration for dust. One big fan at one end can create a negative pressure that makes doors hard to open and drags odours exactly where you don't want them.

What most people don't realise is that the biggest heating problem in these buildings isn't the outdoor temperature. It's the loading doors opening and closing all day. A 5 m × 4 m door opening can dump a huge volume of cold air into the space in seconds. A bigger space heater won't fix that. A fast-acting air curtain or radiant heating system will.

My rule of thumb for a waste transfer shed is to aim for 4–6 air changes per hour as a starting point, then confirm the number with an engineer who knows the local setup. In the UK, ASHRAE Standard 62.1-2022 is a good reference for acceptable indoor air quality in industrial spaces. I'm not going to pretend there's a single rule that fits every site.

And please: don't use portable space heaters in these spaces. I know the appeal—they're cheap, easy, and instant. But in a dusty, draughty environment, they're a fire risk and an energy black hole. I've seen the scorch marks. You don't want to see them on your insurance claim.

Scenario B: You need a bathroom exhaust fan in a commercial building

If the space is a bathroom, changing room, or shower room, the priority is moisture and odour, not dust. But people assume any bathroom exhaust fan will do. What they don't see is that the fan is only half the system. The duct run, the terminal, and the control matter just as much.

In 2018, I specified a small domestic extract fan for a busy restaurant bathroom. It looked fine on paper. It wasn't. By 7 p.m., the mirror was fogged and the smell was drifting into the dining area. The problem wasn't the fan's brand—it was that I'd sized it for the room's average occupancy, not the peak load. We replaced it with a 150 mm centrifugal fan running on a timer and a humidity sensor. The fix cost more than the original fan. That's mistake number nine.

For commercial toilets in the UK, Building Regulations Approved Document F (2021 edition) gives a useful starting point: a minimum extract rate of 15 litres per second per WC or urinal, or six air changes per hour. Your local building control officer can tell you which applies to your project.

One more thing: if the bathroom is mechanically ventilated and the building is heated, an energy recovery ventilator can recycle the heat from the exhaust air. Otherwise you're literally pumping warm air—and your heating bill—outside every time the fan runs.

Scenario C: You're trying to program a Honeywell thermostat (or choose between a thermostat and a space heater)

If your problem is a heating system that runs when it shouldn't, you don't need a new fan or a new heater. You need a better schedule.

In February 2024, a client told me their heating was “broken” because the office was freezing at 8 a.m. It wasn't broken. The weekend schedule had set the temperature to 14°C, and nobody had adjusted it for the Monday morning. The thermostat was doing exactly what it was told.

If you've been searching for 'how to program honeywell thermostat', here's the short version that works for most Honeywell digital models: press the Menu or Schedule button, select the day, then set the four periods—Wake, Leave, Return, Sleep—and the temperatures you want for each. Press Done. If you have a touchscreen model, look for “Schedule” on the home screen. Honeywell's official support site has model-specific instructions if your menu looks different.

And here's the contrarian bit: you don't need a smart thermostat to get most of the savings. A correctly programmed standard thermostat will do the bulk of the work. The smart upgrade is nice if you want remote control, but it won't magically fix a schedule that doesn't match your routine.

So where does a space heater fit in this scenario? As a temporary booster, not as a replacement. If your main heating is off overnight, an office space heater running for one hour can take the chill off before the set point rises. But leaving a space heater on all day because the thermostat is programmed wrongly is just paying for the same waste twice.

How do you know which scenario you're in?

Take thirty seconds and ask yourself these three questions.

1. What are you actually fixing? Dust, volume, and loading doors on a large open space → Scenario A. Damp, smell, or fogged mirrors in a small room → Scenario B. A heating system that runs at the wrong time → Scenario C.
2. What's the room doing? Big doors opening constantly and waste being moved around? That's not a bathroom problem and it won't be solved by a thermostat. Be honest about the space you're in.
3. What's your budget? If it's under £500, you're almost certainly in Scenario B or C. If it's over £2,000, spend a fraction of that on an hour of engineering advice before you buy equipment. That advice will save you from making the same mistake I made.

That's it. No universal answer, no magic box, no “best” space heater that's actually best everywhere. Just a clear-eyed look at the space and the problem.

Before you buy anything, run this checklist:

• Define the problem in one sentence.
• Measure the space—length, width, and height.
• Check the relevant standard or building regulation.
• If it doesn't feel obvious, talk to an engineer.

I've spent 14 years and roughly £86,000 learning that the product is never the starting point. The scenario is. Now you know which one you're in.