Renovation & Design


Renovation & Design

Heat-recovery ventilator should handle steam-shower moisture

QUESTION: I just purchased a 10-year-old house that has a Lennox HRV unit. I want to convert a bathroom tub and add a steam shower. Is the HRV sufficient for the steam or do I require an exhaust fan? If so, the problem is that it is in the fully finished basement.

— Donna Bradley Katz

Answer: The heat-recovery ventilator (HRV) installed in your home should be sufficient to remove the steam from the new shower, as long as the system is designed and installed correctly. This should be easily evaluated by a licensed HVAC technician, who may be able to make modifications, if required, to ensure it works effectively.

HRVs are designed to provide proper ventilation for new homes, as well as reducing relative humidity (RH), by exhausting damp air from several areas in the home and replacing it with dryer outside air. The main areas of moisture generation are the bathrooms, due to water vapour created primarily from bathing and showering. If the system is designed and set up properly, a timed switch in the bathroom should be manually engaged that will run the unit on high speed, when required. By activating the switch before you use the retro-fitted steam shower, it should draw the saturated air in the bathroom into the register mounted on the wall or ceiling in the bathroom. This will move the moist air through the ducting to the HRV unit, where it will be passed through the heat-recovery core, before venting to the exterior.

The HRV should already be adequately sized for your home, and the only concern with additional moisture generation from the steam shower would be that the unit runs for a longer period of time to accommodate it. It may only take a few minutes to clear the damp air from your current bathroom after a shower.

The damp air will likely increase significantly with the new steam-generating unit. Since most bathroom HRV controls are timed to run for a minimum duration before automatically shutting off, you may only have to check to ensure your control time is adequate. In fact, many of these controls have multiple choices for run times, so setting it at a longer run time may be all that is required to properly dissipate the additional water vapour.

One thing to ensure is that the HRV unit is properly balanced, no matter what your decision is with the steam shower. This technical adjustment needs to be done by a trained professional, with specialized equipment.

Balancing is primarily ensuring that when the unit is running, the same amount of air enters the home as is being exhausted. This can be adjusted by use of a balancing control, which will ensure your home is not placed under negative or positive air pressure due to the operation of the HRV. An HVAC technician who installs HRVs should have the testing equipment available, but requesting this specialized service should be done when booking an appointment.

The other item to check is the dehumidistat function on the main HRV control, normally located near the thermostat on the main floor. This control will have a dial or other method of setting the desired RH in the home, before the HRV unit engages. This should only be used in the heating season, but should also help prevent moisture-related issues with the new steam unit.

If you set this control to a normal winter setting, typically around 30 per cent RH at room temperature, it will engage the HRV if the indoor humidity gets too high. This may help if the steam shower is raising the RH in the home, even temporarily, when in use. Also, using this in the winter may help prevent condensation on windows and other basement cold areas, preventing mould growth.

The last thing to be aware of is that the HRV will not only help control air moisture levels in the bathrooms, it will work for the entire home, if the dehumidistat is functioning and used. Since there are additional registers near the kitchen, possibly the laundry room, and all the bathrooms, damp air will be removed from all these areas whenever the unit turns on.

So, if you have a small amount of residual moisture or condensation in the basement bathroom well after showering is complete, this may be removed when a control is activated in another area. This may be done with a manual control in another bathroom, or the main control through the dehumidistat function. This is why there is a register near, but not normally inside, the kitchen.

If the range hood over the stove is not successful in removing all the moisture from cooking or sink use, the HRV should help when the RH on the main floor exceeds the setting.

Additional moisture control in your basement bathroom should be no problem for your existing HRV unit, as long as all the controls are functioning properly and used. Calling a licensed HVAC contractor to check it all out should ensure it prevents excessive condensation and mould growth in the home due to the renovated bathroom.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba ( Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at


July 13

Renovation & Design

Use sandpaper on Tyndall stone buildup

Question: We have a front bow window under which is Tyndall stone. The window ledge and the stone under the window have turned black. What is the best remedy for removing the unwanted buildup? If it is better done professionally, please recommend the type of company or profession that would be able to help.

— Gary

Answer: If the surface is smooth, your best bet is to sand any stained areas with 50-grit sandpaper. A belt sander is a little easier and will save time. Do not use TSP on the surface; because of the salt in TSP, you may end up with white residue (efflorescence) on the stone. If the stone is rough, clean with a nylon-bristle brush. In both cases, avoid using water, but if you feel that it is very necessary, protect the surrounding area and clean with 50/50 bleach and water. If you decide to enlist professional assistance, please contact a quarry or limestone specialist in your area.


Question: I baked a chocolate cake from scratch and put a baking sheet underneath just in case the batter leaked out of the pan. I baked it for about a half-hour and tested it with a knife to see if the knife came out clean; it did. When I sliced the cake after it had cooled, the middle section was still sticky and doughy. What a mess! Is there anyway to save this cake or is it garbage?

— Lorne

Answer: Throwing out a plate of chocolate is like throwing out a plate of happiness; it’s just so sad. Here are two ideas that will save your dessert. Make a trifle. Chop up the entire chocolate cake into bite-size nuggets of goodness. Place the pieces into a large glass bowl. Add chocolate pudding, cut up strawberries and whipped cream. Garnish with shaved chocolate. Second idea: cut out the centre of the cake to make a ring cake. Melt chocolate chips or chocolate squares in a double boiler. Pour onto the top of the cake ring, allowing the chocolate to run down both sides of the cake. After the chocolate has hardened, serve. I think I just heard my stomach growl.


Get the wooden spoon

I always found it challenging when making a bed to tuck the sheets under the mattress. I discovered that if I use a wooden spoon to push the sheets under the mattress, the job becomes a cinch.

— Laurie

I read this tip in a book years ago, tried it and it worked. Place a wooden spoon in a pot of boiling water while cooking pasta, the pasta won’t stick together.

— Brian

I always use a wooden spoon when planting the garden. Mark the handle with a permanent marker and then push the handle into the soil as a guide, so that all seeds are planted at the same depth.

— Leroy

Note: Every user assumes all risks of injury or damage resulting from the implementation of any suggestions in this column. Test all products on an inconspicuous area first.

Reena Nerbas is a popular motivational presenter for large and small groups; check out her website: Ask a question or share a tip at

Reena Nerbas
July 6

Renovation & Design

Go with high-quality pleated filters

Question: We’ve had many warmer winters since 2008 and the HRV intake frost problem described to you then was not always apparent, but in 2017, we happened to be home all winter and the old problem reared its ugly head again. This was long after your advice was followed to have the furnace/HRV installer check all fittings for the intake and exhaust hose. No air leaks were found, but hose connections were all resealed with tape.

I removed the quarter-inch wire mesh from the HRV intake hood and enlarged the mesh openings to a half-inch, to no avail. I then purchased mesh with three-quarter-inch openings and installed it, also without success. Eventually, I installed mesh with one-inch openings, with the same results. When the temperature drops below the -25 C range, the mesh plugs up solid with ice crystals within 24 hours after cleaning it.

I made a much larger rodent mesh with half-inch square openings. I don’t know what the smallest proper size would be to make this work, so I chose to make it bigger instead of smaller. And when the temperature was -25 C with over 50 per cent humidity outdoors, there was no sign of buildup of ice crystals anywhere on the rodent guard. I also added spray foam around the HRV intake hose between the joists, even though that had been done professionally at the time the house was built in 2007.

Now, on to the next tough question: what is your opinion about furnace floor-vent filters to reduce dust in the house? We had one bad experience with furnace duct cleaning and don’t relish the idea of doing that again. Are there other ways to reduce the floating and circulating dust in the house? We have an electronic air cleaner that is cleaned regularly, which doesn’t seem to be adequate.

Thank you in advance.

— Lawrence Klippenstein

Answer: It is always nice to hear an update on advice from a previous column. Also, using floor-vent filters may help a little in reducing dust, but the best option is to replace your electrostatic filter with high-quality disposable pleated filters, which are changed frequently. That will be a lot less effort and should work just as well, if not better.

I suspect changing the mesh size on the HRV intake-vent hood may have had some benefit in reducing or preventing frost accumulation, but the upgraded insulation may be the true saviour. If the existing fibreglass insulation, wrapped in plastic, was wet, damaged or had holes, warm air from the home may have leaked into the duct. If this warm, wet air contacts the incoming cold air, condensation is almost certain. Blowing foam insulation around the duct in that area may have helped prevent any warm-air leakage, minimizing the moist air that causes the frost.

As for installation of individual filters in floor registers for your heating system, I don’t think there would be much opposition from HVAC contractors, as long as you did not want them to install these items. There are no pre-manufactured filters that I know of and all would have to be retrofitted by cutting some form of filter material or fabric to fit each register or heating boot. During the course of regular pre-purchase inspections, I have seen some homeowners attempt this, presumably by themselves, but I don’t know if they have been effective. On the other hand, if you have a small electric air filter, which slides into a standard one-inch slot in the return-air ducting, then changing that may be the simple answer.

Most of the one-inch-thick electrostatic filters I see are not functioning properly or effectively. This could be due to poor maintenance and cleaning by the homeowners, but more likely, it is inherent in the products. Any type of furnace filter designed to be cleaned may be subject to poor performance over time, due to typical wear and tear or just a lack of attention to detail. Once dirty and plugged up, these filters may never regain their original performance. So, unplugging your unit and replacing it with a high-quality disposable pleated filter should be the simplest and least costly option. You will have to remove, discard and replace the filters every couple of months, but that may be a small cost for the improvement in dust management.

Putting individual filters on all the registers in your home will be a very time-consuming effort, at moderate cost, especially if you replace them regularly. You are probably much better off tossing out your old cleanable electrostatic filter and using regularly replaced, inexpensive pleated filters to prevent excessive dust in your home.

Ari Marantz is the owner of Trained Eye Home Inspection Ltd. and the past president of the Canadian Association of Home & Property Inspectors — Manitoba ( Questions can be emailed to the address below. Ari can be reached at 204-291-5358 or check out his website at


Ari Marantz 
July 6

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