Subfloor Ventilation FAQ / Information




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How do I calculate the size of fan I need for my Underfloor Area?


We base our recommendations on achieving 5 air changes per hour.  This means exhausting the underfloor area’s overall volume 5 times per hour. In most cases, this is enough.

This is easy to calculate. All you need to do is measure the size of your subfloor space in m3 (length x width x height). Then take this figure and multiply it by 5:


My subfloor area is 50m3 – 50m3 x 5 = 250m3

So you need to find a fan that exhausts approximately 250m3/hr

Please note: This is a rough estimate applicable for most situations.

Why don’t your systems mechanically pull fresh air into the house?


At Subfloor fans warehouse we always recommend exhausting the air from under the house rather than pushing it in. This is because when air is pushed in it sometimes finds its way into the house through floor gaps, gaps in floor vents, under doors etc. Exhausting the air through a ducted system via a vent you can ensures it is expelled properly. This ensures efficiency and optimum effectiveness.

Why should I buy a system from Subfloor Fans Warehouse?


Our kits are designed for DIY Installation.  So if you have access to your sub floor space, a power point under the house and some basic DIY skills you can install these kits easily.  For this reason, our systems can work out to be much cheaper than alternatives that may require a site visit and costly installation fees. Ultimately, we want to provide the Australian public with the products and resources to perform this job DIY.

We provide the highest quality components. Our Subfloor kits all include high quality fans, many with German made ball bearing motors, specifically engineered for continuous operation and long life.

How many hours do I need to have a subfloor fan running?


We have found that operating the fan for approximately 4 hours per day is sufficient to maintain good ventilation. Generally its best to have the fan running during the day when the air is dry and warm. Running the system during the day also means the fan’s sound is less of an issue. The most convenient way of running the fan for a predetermined number of hours is by using a simple plug in timer. All of our subfloor kits come with a 24 hour timer.

If you have particularly bad problems then you may need to initially run the system for longer than four hours. Of course, each situation is unique so it’s difficult to give exact advice. To start with, try running the fan  for between 6 and 12 hours and monitoring the situation. As things begin to improve you can lower the amount of hours the fan is operating.

How much does a Subfloor fan system cost to run?


sub floor fan cost

Typically subfloor systems are energy efficient – to calculate the annual cost of operating one, look at the motor wattage. As a rough estimate a 100w motor will cost approximately $51 to run annually, for 4 hours per day. This is less than 98 cents per week. To make things easier for you we have provided the approximate annual cost on each of our subfloor kit listings.

All figures provided by Subfloor fans warehouse are intended to give you an estimation, they are not intended to be 100% accurate as actual costs will vary depending on your usage amount and individual electricity rates. All rates are calculated using a rate of 35 cents per 1000w per hour. This is an average ‘peak rate’ at the time of printing (2014). Calculations are based on peak rates as generally these systems will be operating during the day.

How noisy is a Subfloor System?


The noise will vary depending on the size of fan used (each fan has a dBA rating). The general rule of thumb is the larger the capacity the more noise generated from the fan. Generally speaking, fans are pretty quiet. Switch them on during the day to avoid making noise at night. The floor will also insulate some of the noise. You can also offset noise if you think carefully about where you place the fans. Putting them under unused rooms limits the noise you hear during day to day activities. Consider this when you install your system.

Would I be better off installing a solar powered subfloor fan?


Although Solar powered fans are undoubtedly lower in running costs, they are not always the best solution. Firstly, Solar powered units (fan + solar panel) are much more expensive to buy in terms of initial cost. In most instances, installing solar panels on the roof is a complicated process. Running cabling from the roof to the subfloor is also difficult, especially if you already have a power point under the house.

Solar units generally have a much lower capacity, which may not provide enough air movement for a large subfloor area. Finally solar powered subfloor units without a battery will only operate when the sun is shining, meaning they will not run or will run very slowly if it is cloudy.