EPDM roofing in Silver Spring, MD: what Maryland's energy code says about the insulation under the rubber

Zone 4A and the numbers that follow

Maryland's energy code is the 2021 International Energy Conservation Code with state amendments, and Montgomery County's permit office lists the 2021 edition on its master list of codes. The copy read here is the third-party UpCodes version, so confirm the edition and any county change with the Department of Permitting Services. Its climate zone table puts Montgomery County in zone 4A, and every figure below is the row for that zone.

The code has a commercial part and a residential part. Apartment buildings, offices and shops are not read the same way as a detached house or townhouse, and the pages read here do not decide which part a given Silver Spring building falls under. That is a question for the county before any scope is written.

Residential and commercial values compared

UpCodes copy of the Maryland Energy Code 2021, read October 20, 2026. The "ci" means continuous insulation, laid over the deck without gaps for framing.

The commercial text says continuous insulation layers are summed, and that cavity insulation does not count toward the continuous requirement. For a flat roof where the board sits above the deck, the thickness of every layer of board therefore adds up toward the listed number. For board above the deck, the residential text lets the R-value be labeled under the material standards in its roof insulation table.

What a re-roof triggers in the energy code

1. Commercial replacement section C503.2.1 says a roof replacement meets the roof insulation sections where the existing roof is part of the thermal envelope and has insulation entirely above the deck.
2. No step backward the same section says the R-value of the roof insulation may not be reduced, or the assembly U-factor increased, by a replacement.
3. Recover and repair the existing buildings chapters list a roof recover among work not held to the new-construction values, and list roof repairs as repairs. Air barriers are not required for either when the rest of the envelope is untouched.
4. Residential cavity roofs the residential text says a roof without insulation in the cavity, where the sheathing or insulation is exposed during reroofing, is insulated above or below the sheathing.

Read together, a tear-off to the deck on a building that already has board above it is a different question from coating or recovering. The text does not define the words for a given scope, and the county's Home Improvements page lists "Roof (covering only)" among work most likely to need no permit while saying exempt work still has to meet the code. Ask the county where your job falls. The Silver Spring hub sets out who signs in a house, a condominium and a rented building.

Polyiso boards, layers and thickness

The guide also says to offset seams in two directions between layers, run a sealant bead at the perimeter, tape the seams, and slope low-slope roofs to drains at not less than a quarter inch per foot.

Fastening through the insulation

A mechanically attached sheet is held to the deck by fasteners that pass through the board. The Maryland building code text read here does not give a fastener count. It says coverings that are mechanically attached or adhered to the deck are designed to resist the wind pressures set for components and cladding, and that fully adhered or mechanically attached single-ply systems are tested under FM 4474, UL 580 or UL 1897.

• The code text read here points to component and cladding wind pressures and gives no single figure for a given roof.
• A tested assembly is chosen whose layers match the job: deck, board, fastener, membrane.
• SPRI says its online Directory of Roof Assemblies lists low-slope systems tested for uplift, edge securement and impact, searchable by assembly composition.
• The scope then repeats that assembly, so the fastened layers on the roof match the layers that were tested.

This page does not give fastener counts or spacings, because no document opened here sets them. Ask for the tested assembly in writing.

Items to put in the EPDM contract

Roofers of Arlington installs, repairs and replaces roofs, including flat systems. To talk through a Silver Spring EPDM roof, book a phone consultation. On the call the questions would be the address, the building type, who owns the roof and what is visible. See also the EPDM guide, flat roofing, commercial roofing, roof replacement, materials and services.

• Which part of the energy code the county applies, and which value in the table the design meets.
• The board type and standard, the facer, the thickness of each layer and the number of layers with staggered joints.
• The thickness at the drains, scuppers and edges where board tapers.
• Whether a cover board goes in, and the membrane maker's written word on the pairing.
• The tested assembly record the fastened layers match, and who set the wind pressure.
• Whether the work is a replacement, a recover or a repair, in the county's words.
• Who else must approve: association, Takoma Park, the historic office.

Owner

The household, the council of unit owners or the landlord signs.

Office

Ask the county, your association and your engineer. Nothing here is legal or engineering advice.