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Making attic warm storage

  • 08-01-2022 2:25pm
    Registered Users Posts: 40

    I'd like to improve the insulation in my attic so that it is essentially a warm storage space.

    As you can see from the pictures, I'm in the middle of flooring the remaining crawlspaces having put an additional 200mm Metac insulation over existing 200mm insulation.

    There is good depth in the rafters at about 200mm. Is it ok to put in 100mm insulation between these rafters - and should I go for rigid board insulation or roll? I already have 100mm insulation above the top floor ceiling - which you can see in the 3rd pic, so I was thinking off running the additional 100mm between the rafters up to meet this.

    Is there anything I need to consider when adding in this extra insulation?

    Thanks for any direction

    Post edited by irewestlad on


  • Registered Users Posts: 2,524 ✭✭✭Yellow_Fern

    I am not an expert but with rolls you wont get anywhere the ideal U value. With boards it is very hard to get a tight fit and the tight fit is all important. Also critical to leave a ventilation gap in between the insulation and the felt. I think it has to be 5 cm but check.

  • Registered Users Posts: 40 irewestlad

    Thanks @Yellow_Fern. if I put in 100mm, I would still have another100mm to the felt, so perhaps I should be increasing what I put in to about 150mm

  • Registered Users Posts: 2,758 ✭✭✭MicktheMan

    What do you mean by a "warm storage space"? How will it get warm?

  • Registered Users Posts: 751 ✭✭✭C. Eastwood


    I do not understand what you are trying to achieve in your attic.

    The Building Regulations (BR) 2019 require Ventilation of the roof void of a domestic dwelling.

    The minimum ventilation requirement are set out in Technical Guidance Document (TGD) F Ventilation. - here is the Diagram 11- Ventilation of Roof Voids, from this document- which shows the minimum requirements.

    If what you wish to do is not shown here, then do not construct it.

  • Registered Users Posts: 4,161 ✭✭✭beggars_bush

    they need to update those diagrams for buildings with no soffit

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  • Registered Users Posts: 751 ✭✭✭C. Eastwood

    No need to update these Ventilation Regulations

    The Designers of Dwellinghouses must comply with these Technical Guidance Documents of the Building Regulations

    If the Clients decide not to fit Soffits, then the Designer can comply with the TGD Ventilation- by installing ventilation in the Fascia and / or Eaves etc.

  • Registered Users Posts: 40 irewestlad

    Thanks for the responses.

    Here's what I was trying to achieve. My office is on the top floor of my house. I have crawl space either side of the office. I have DIY insulated the side walls and above the ceiling, and upped the attic insulation to 400 mm before putting down flooring on top of risers. My thinking was if I insulated further between the rafters (in red in the diagram) it would add an additional layer of insulation to keep the office warmer. Would this be the right approach?

  • Registered Users Posts: 2,758 ✭✭✭MicktheMan

    "My thinking was if I insulated further between the rafters (in red in the diagram) it would add an additional layer of insulation to keep the office warmer. Would this be the right approach?"

    It won't do anything for heat retention of the office and may even compromise the roof ventilation.

    Your likely issue with heat loss in this space is a lack of air tightness (aka draughts) rather than a lack of insulation.

  • Registered Users Posts: 3,027 ✭✭✭Lantus

    Your crawl space should be vented by gaps at the eaves. This allows outside air to circulate and prevent condensation. Yes you can add insulation as shown but you are essentially building new walls like your office. So you need a gap between the board and felt. And you don't go into the corner. You will drop vertically near the lower part of the roof. But without being plastered and heated and without a window to ventilate you will run into issues.

  • Registered Users Posts: 40 irewestlad

    Ok great, thanks all for the feedback

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  • Registered Users Posts: 38,466 ✭✭✭✭Mellor

    They are examples. Not the extent of everything that’s possible.

    Buildings must comply with Buildings Regulations. TGDs are guidance on how to comply with the building regulations, but they are not part of the building regulations themselves.