Last July, a two-bedroom condo in downtown Toronto faced a week-long stretch of humid heat: daytime highs of 30-32 C, overnight lows stuck around 23 C, and relative humidity hovering near 65-70%. The tenant, a small family, found that even when the thermostat read 27 C, the apartment felt much hotter and sticky. Running the central air conditioner all day was noisy, costly, and still left bedrooms clammy at night.
This case study follows what they tried, the simple technologies and controls they added, and the measurable outcomes over 60 days. The main idea: in many parts of Canada during hot, humid spells, reducing indoor humidity can produce a bigger comfort gain than lowering air temperature a degree or two. Getting humidity under control changed how cool the space felt, cut AC runtime, and lowered monthly power bills.
Why High Humidity Made 28 C Feel Like 34 C
Indoor comfort depends on both temperature and humidity. The condo’s initial conditions were:
- Indoor dry-bulb temperature: 27.8 C (evening average)
- Indoor relative humidity (RH): 68%
- AC runtime: about 10 hours per day during the hottest stretch
- Monthly electricity increase vs. baseline: approximately CAD 85 for that period
At 68% RH, sweat does not evaporate efficiently from the skin, which raises perceived temperature. The family reported feeling “suffocating” and used fans together with AC to try to get relief. That combination was noisy and still uncomfortable. They faced two core problems:
- Their AC was cooling but struggling to remove enough moisture, because the system is sized for sensible cooling and not always optimized for latent load (moisture).
- Running AC full time created cold nights in some rooms and left other rooms with uneven humidity – bedrooms stayed humid and clammy even with the unit on.
Consequences included more mold risk in the bathroom and closets, restless sleep, and rising electricity bills. The family wanted a solution that improved comfort, reduced AC run time, and didn’t require replacing the central AC immediately.
Swapping Constant AC for Targeted Dehumidification and Cross-Ventilation
Instead of immediately replacing the HVAC, they tested a strategy combining targeted dehumidification, improved airflow, and smarter control of the AC:
- Deploy portable refrigerant dehumidifiers in the most humid zones (bedrooms and living room).
- Use ceiling and portable fans for air movement to enhance evaporative cooling from occupants.
- Adjust thermostat strategy – raise temperature setpoint slightly while maintaining RH below 50%.
- Improve passive ventilation at night when outdoor RH was lower by opening windows strategically.
- Monitor with humidity sensors and record AC runtime and energy use.
Key reasons for this approach were cost, speed of deployment, and the expectation that reducing RH from the high 60s to the mid 40s would produce a perceived temperature drop equivalent to 2-4 C without overcooling the space.
Why a dehumidifier can feel like cooling
Dehumidifiers extract moisture (latent heat) from air. Removing moisture helps sweat evaporate more readily, so people feel cooler at the same air temperature. Note that a dehumidifier rejects heat to the room as part of its operation, so room air temperature can rise slightly. The net effect on comfort comes from the humidity drop, not from lowering dry-bulb temperature.
Installing and Tuning the System: A 60-Day Roadmap
They implemented the solution in a staged 60-day plan so they could measure results and tweak settings. Here is the timeline with specific steps and costs.
- Purchased two portable refrigerant dehumidifiers: one 30-pint (approx 14 L/day) for the living room ($220) and one 50-pint (approx 23 L/day) for the bedroom zone ($420).
- Installed two inexpensive digital hygrometers ($25 each) in separate zones and a plug-in energy monitor for the AC ($60).
- Recorded baseline: RH 66-70%, AC runtime 10 hours/day, estimated daily AC energy 22 kWh on hottest days.
- Set dehumidifiers to 48% RH with built-in humidistats. Placed units near humidity sources (bathroom door and bedroom hallway) and ensured unobstructed airflow.
- Raised thermostat setpoint from 23.5 C to 25.5 C during daytime; used a 1 C setback at night to keep sleeping comfort. Fans set to medium for cross-breeze.
- Recorded daily RH, AC runtime, and approximate kWh. Noted small rise in living room air temp of 0.4 C where the dehumidifier ran most.
- Programmed dehumidifiers to run on a schedule: daytime priority for living room unit, evening/night priority for bedroom unit. This matched occupancy.
- Set up a simple gravity drain to the laundry sink for the living room unit to avoid bucket changes.
- Monitored noise and moved units slightly to reduce nighttime disturbance. Cleaned inlet filters after 2 weeks.
- Swapped bedroom unit to continuous operation on high humidity nights and lowered setpoint to 44% RH in the bedroom to improve sleep quality.
- Opened windows at night for two hours when outdoor RH dropped below indoor RH and outdoor temp was comfortable, to purge latent load without using AC.
- Collected final 30-day metrics and compared to baseline.
From Sticky 68% RH to Comfortable 44% – Measured Gains in 30 Days
After 30 days of the tuned dehumidification strategy, the family tracked these concrete results.
Important notes about the numbers:
- The perceived temperature calculation combines dry-bulb temperature and RH; feel is subjective but both occupants and a simple heat-index calculation matched the reported comfort gain.
- Energy figures were measured with a plug-in meter on the AC and dehumidifiers and validated against the utility bill. Dehumidifiers used roughly 0.55-0.65 kW when running. Their additional electricity use was outweighed by AC reduction.
- There was a small rise in measured dry-bulb temperature in rooms near the dehumidifiers, but the drop in humidity more than offset that for human comfort.
5 Practical Lessons From One Condo’s Summer Experiment
These are the hard-won insights that matter most when you try this in your own place.
Advanced tuning tips
For people ready to go beyond plug-and-play, consider these techniques:
- Install a whole-home dehumidifier integrated with your HVAC if you have chronic humidity across the building – initial cost is higher (CAD 800-2,500 installed) but control and distribution are superior.
- Use a smart humidistat and schedule dehumidification around occupancy and outdoor conditions. This limits runtime during cool, dry nights when window ventilation is preferable.
- Consider desiccant dehumidifiers for very low-temperature or high-ventilation situations – they handle low temps better but are less common in residential settings.
- Coordinate with HRV/ERV settings – these systems can be adjusted to exchange more or less air based on humidity, which reduces indoor humidity without mechanical dehumidification in some conditions.
Could This Work for Your Home? A Quick Self-Assessment and Step Plan
Not every home will get the same gains. Use this short quiz to see if targeted dehumidification is a suitable next step. For those concerned about financial planning, you may also want to learn about Life Insurance to Cover Student Loan Debt: What You Need to Know.
Quick Self-Assessment
- Yes – 2 points
- Sometimes – 1 point
- No – 0 points
- Yes – 2 points
- Occasionally – 1 point
- No – 0 points
- Yes – 2 points
- Minor spots – 1 point
- No – 0 points
- Yes – 2 points
- Sometimes – 1 point
- No – 0 points
- Yes – 1 point
- No – 0 points
Scoring cost of running ac guide:
- 7-9 points: High chance this approach will help. Consider a 50-pint unit for sleeping zones and a 30-pint for living spaces.
- 4-6 points: Moderate chance of benefit. Measure RH and try a portable 30-pint unit first.
- 0-3 points: Low likelihood this is the root cause. Look at insulation, HVAC balance, and window shading instead.
Step Plan to Try This in 7 Days
If you try this and want help interpreting your readings or optimizing placement, share your humidity numbers, apartment square footage, and AC model and I’ll help tune a plan that fits.
In this Toronto condo, targeted dehumidification turned a miserable, sticky summer into comfortable nights and lower bills without costly HVAC replacements. The strategy is not a universal cure, but when humidity is the main culprit it can transform how cool your home feels.
