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Re: [EnergyPlus_Support] Insulating wooden floor raised 400mm from ground in temperate climates

I thought the use of the wooden floor was exactly because it's not as cold as tiles. This was the reason my mother bought wooden toilet seats.

The fact that it is raised, is to ensure that it remains properly ventilated to avoid wood rotting do to moisture problems. I think the key here is to ventilate under the wood during the day and not during the night. The low temperature of the floor stems from the ODA ventilation. It certainly does not stem from 1) a cold night sky radiation or 2) the temperature of the earth underneath. The old houses are usually very massively build and have a huge internal mass.

In the house I mentioned were I grew up in South Africa, the mornings in winter would easily be 5 degC...I experienced many at -6 degC...and on the same day the maximum temp would raise to 18 degC. This was not exceptional, but the norm. The climate is considered temperate. This means less extreme temperatures but the daily temperature swings are much more. Summer 18-24, Winter 5-18. Australia is a bit more extreme, but not much. Summer 18-36, Winter 5-20.

Only hotels had heating... Culturally, we were used to sitting in a cold house with a portable heater or simply wearing our coats inside. No body had heating. I'm now in Germany and my wife is often telling me to take off my jacket as it makes here feel as if I'm busy leaving to go somewhere. We would also use rugs in South Africa. The toilets would sometimes have cork tiled floors as a warmer alternative to ceramic, or for the newer homes very seldom floor heating. Solar hot water heating systems with evacuated pipes is common now. There is so much sun in SA and Aus that it is almost stupid not to have this. My parents installed these systems during the power outages of 2006 along with a backup generator in the garage.

The newer, less massive building styles suite this climate badly. with the high temperature variation over the day, there was a lot of comfort from the house temperature. the same is true of the increased window to wall ratio trend. Our house was always warm in winter and cool in summer...it was old style built in 1907.

Keep us posted what you decide.

For modelling, I would suggest modeling the floor cavity as a separate zone and not use the default convection calculation algorithms but those suited to small cavity spaces. You can now apply this to only this zone.

On 17 November 2012 20:38, YuanLu Li <yli006@xxxxxxxxxxx> wrote:

HI, Dr. Ooi

There are  lots of suggestion given by Jeremiah below.  He is a PCM expert.   Are you going to try any of them to satisfy your appetite for comfort/energy savings?


 Dr. Li  


To: ooi_kb3@xxxxxxxxxxx; EnergyPlus_Support@xxxxxxxxxxxxxxx
From: jcrossett@xxxxxxxxxxxxxxx
Date: Fri, 16 Nov 2012 18:27:18 -0800
Subject: RE: [EnergyPlus_Support] Insulating wooden floor raised 400mm from ground in temperate climates

Closed cell spray foam with R value of 7.2 per inch, adding Resistance does very little after  so apply about 8 inches. This will provide a tight air seal so to model it use AFN and reduce the surface crack CFM to near 0. If the foam is light in color set the solar absorbance to a realistically low value. (if exposed this will reduce heat gain from long wave solar radiation)  Set the roughness to smooth. Use conductivity,specific heat and density of similar type of foam.(from HOF materials dataset) Spray foam applied to the exterior does not have thermal bridgeing, while inside applications require an assumed increase in conductivity. Use cost object and apply a bidded cost for construction. Based on fanger PPD, surface temperatures, energy savings, energy value and client appetite for comfort/energy savings and first cost adjust the insulation the thickness.

Sent from my Windows Phone

From: Ooi
Sent: 11/16/2012 3:43 PM
To: EnergyPlus_Support@xxxxxxxxxxxxxxx
Subject: [EnergyPlus_Support] Insulating wooden floor raised 400mm from ground in temperate climates


i have a 12 m x 12 m single storey with wooden floor. This house is located 37.7 degrees south of the equator on the eastern side of a very big land mass. The temperature and wind varies widely, and this location is tooted to have 4 seasons in a day. Its getting expensive to maintain and operate a gas heater with ducts to the 6 compartments of this 54 yr old house.

The floor is raised 400-500mm above ground level. The house is of brick veneer and the bricks go down at least have a meter into the ground. Dr Li suggested 1 m insulation around the perimeter both horizontally and vertically. Since the air space below the floor is vented to the outdoor air which can go down to 5C in winter months, i doubt this is sufficient to make the occupants not having to wear socks or slippers.

i am also looking for economical floor insulation for a proposed 6.3m x 3.4 m nanny house separate to the above building. Any better suggestion than looking for cheap underfloor insulation/s?

All the best to everyone, ooi


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